Home

User Manual for the Potential Water Retention Model (PWRM)

1. ens Existing County Po Watershed Area Acres lz Results Basin Number of Basins E New f Existing Copy Pre to Post Wiha Switch between Pre 4 Past nee Ditch Storage Impoundment Landuse Basin Stage Area Imp Stage Area Trend Analysis Horizontal Seepage Vertical Seepage Structures Open Channels Culverts Weirs Pumps Number of Open Channels Number of Channels Recorded 1 Ad Modify Delete Channel Number Mame T Top of Bank Elevation Feet Top Width Feet i Channel Depth i Feet lm Side Slope t H 1V Feet r o j Longitudinal Slope Feet i Foot lz Manning s Coefficient poe Receiving Body Channel Figure 11 Structures Open Channels Page 46 13 Select the Number of Open Channels you want to enter from the drop down list For each channel enter a Channel Number Name identifying it It is recommended the channels be given meaningful names if possible to facilitate future data review The Top of Bank Elevation Top Width Channel Depth and Side Slope should all be based on field review of the channel at a location far enough upstream of the outfall so as to be away from tailwater influence Tailwater elevation data can be provided to the model using an Input file in the Client Data workbook Open Channel TW worksheet If this information is not provided the model will assume the tailwater elevation 0 0 ft This same t
2. Vertical Conductivity Feet Day Head Feet Aguitand Thickness Feet 1 Basin to Aquiter Modify Delete 2 Impowndment to Aquiter Continue Figure 10 Vertical Seepage Page 45 judgment The user can enter each interface only once by selecting the interface entering the data and clicking the Add button on the bottom left side of the screen If you are editing a basin previously entered or need to change any data just entered select the interface you want to modify from the Interface Type drop down list and then use the same processes previously described to Modify or Delete Click on the Continue button or the next tab to move to the next screen 12 Structures Open Channels Figure 11 This is the eleventh tab from the left of the row of tabs in the upper middle section of the main screen The Structures tab opens a sub menu set of four tabs representing each of the available structure types The first type 1s Open Channels and allows a maximum of ten channels to be entered If you have more than ten channels you will need to aggregate some by expanding widths and depths to create a single equivalent channel Data Input Florida Ranchlands Environmental Services Program Clear Current Project FRESP PROJECT DATA Val ha i Project Service 4rea Acres PrewhA C PostwhA Meas See Project Basin Basin Area Acres Run the Model
3. M Surface Water Discharge Controls 1 Weir Flow Water can leave the site by surface flow through several mechanisms sheet flow over the site boundary open ditches culverts surface water pumps and weirs Discharge D via a flashboard riser weir is computed based on the rectangular sharp crested weir formula SEWMD 7 D 3 3xLxH 22 Where D discharge feet sec L weir length feet H head over the weir crest feet For V notch weirs the formula becomes D 2 5 x Tan 0 2 x H 23 Where angle of the notch degrees H head of water over the notch feet If the weir becomes submerged 1 e the downstream water level is higher than the weir crest the discharge D will be reduced as follows D D x 1 H H 24 Page 19 Where Hg downstream head feet relative to the weir crest Through the stage storage function the PWRM computes onsite surface water elevations on a daily basis If the user has provided downstream elevations the model will compare the two elevations with the weir crest elevation to determine if submerged flow or reversed flow is occurring Open Ditch or Culvert Flow trough an open ditch or culvert is modeled with the Manning Equation as D A x 1 49 n x A P x S 25 Where A cross sectional area feet n Manning roughness coefficient dimensionless P wetted perimeter feet S slope of water surface feet foot The stage storage function computes the daily on
4. button will overwrite the data currently saved for this basin so do not do this until you are satisfied with all of the breakpoint s and equation s you have selected for this dataset Once you are satisfied with the Storage Stage equations and have saved them click on the drop down arrow in the Select Data to Analyze box and select the Stage Area dataset The Trend Analysis menu will take you through the same process for the Stage Area relationship and then Stage Storage relationship If the project includes an impoundment then after completing the Basin trend analysis you will need to select the radio button for Impoundment and go through the same process for all three relationships separately for the impoundment Click on the Continue button or the next tab to move to the next screen Horizontal Seepage Figure 9 This is the ninth tab from the left of the row of tabs in the upper middle section of the main screen There are six different potential horizontal seepage interface types included in the model calculations These are shown in the graphic on the right side Page 42 of the data input screen numbered 1 through 6 with a legend at the bottom providing a name for each type The names identify the direction of seepage 1 e From To Data Input Florida Ranchlands Environmental Services Program Clear Current Project FRESP PROJECT DATA Wale i Froject Service Area
5. Delete Click on the next tab to move to the next structure type Structures Culverts Figure 12 This is the twelfth tab from the left of the row of tabs in the upper middle section of the main screen The Structures tab opens a sub menu set of four tabs representing each of the available structure types The second type is Culverts and allows a maximum of ten culverts to be entered Select the number of culverts you want to enter from the drop down list For each culvert click on the button representing where the culvert discharges from then enter a Culvert Number Name identifying it It is recommended the culverts be given meaningful names if possible to facilitate future data review Select the culvert Material When you select this the Manning s Coefficient will be entered in the box to the right Page 47 Data Input Florida Ranchlands Environmental Services Program Clear Current Project FRESP PROJECT DATA Val ha Project Service 4rea Acres E Pewa PostwhA A Save Project Basin Basin Area Acres Run the Model f New Existing County poe Watershed Area Acres E Results Basin Number of Basins C New f Existing Copy Pre to Post Wha Switch between Pre Post Eee Ditch Storage Impoundment Landuse Basin Stage Area Imp Stage Area Trend Analysis Horizontal Seepage Vertical Seepage Structures Number of Culverts D Number of Culverts Record
6. MEASURED OR PALEY DATA BASE RAINFALL SFWMD OKEECHOBEE WA RAINFALL ONTO STAGE AREA CURVE y ATMOSPHERIC MOISTURE TER SURFACE is AVAILABLE SOIL STORAGE A RAINFALL ONTO suRrace ee i RUNOFF NRCS SOIL SURVEY MOISTURE LIMITED ET EVAPORATION VADOSE MOISTURE ONSITE SURFAC DEFICIT SURFACE E WATER INFLOW WATER STORAGE MAXIMUM ET SURFACE WATER PUMP PENMAN MONTHLY ET STAGE STORAGE CURVE TYPE OF CONTROL DOWN UP STREAM HEAD OFFSITE DISCHARGE NRCS SOIL INFILTRATION SURVEY DATA IMPOUNDMENT ABOVE GROUND SURFACE DISCHARGE CONTROL LATERAL SEEPAGE VADOSE ZONE NO IS THE WATER TABLE WITHIN THE EFFECTIVE ROOT ZONE IS THE WATER TABLE WITHIN THE EFFECTIVE ROOT ZONE IS VADOSE ZONE FULL ARE THERE ADJACENT i YES i OFFSITE DITCHES i SPECIFIC CAPACITY OF SOIL WATER TABLE amp SURFACE WATER HEADS CONDUCTIVITY DISTANCE NRCS SOIL SURVEY PHREATIC ZONE i NRCS SOIL SURVEY LEGEND PROCESS DECISION DATA EMBEDDED IN MODEL IS THE WATER TABLE AQUIFER CONNECTED TO LOWER UNITS VERTICAL SEEPAGE YES WATER
7. click the Add button To delete an existing connection select the connecting basin from the list of values and click the Delete button The number of interconnecting basins will automatically be updated As interconnecting basins are added in either the Upstream or Downstream boxes they will show up in the list on the right side of the box so the user can see what has already been entered Click on the Continue button or the next tab to move to the next screen Soils Figure 2 This is the second tab from the left of the row of tabs in the upper middle section of the main screen It is recommended that you already have a list of each type of soil in the basin and the number of acres If this is a new basin enter the number of soil types in the first box on the left side of the screen Then in the Soil Types drop down box select a soil type from the list of values Enter the acres for that soil type and click the Add button Note that you can not add the same soil type more than once The box on the right side of the screen will be updated to show the information entered so far The text fields on the bottom left side of the screen are informational and will show the Basin Area entered on the main screen and then a running total of the acreages of soil types entered so far If you attempt to add more soil types than the number entered or have not entered Page 31 as many types as indicated or you have entered a
8. depressional areas are present either in the pre or post WMA condition they are treated separately as impoundments and the following discussion does not apply to them Further pumped above ground impoundments are also treated separately from the rest of the site At any given time a portion of the site will be inundated connected storage and a portion will not vegetated surface The PWRM computes the amount of land that is inundated and the volume of water in the inundated area each day by use of stage storage and stage area curves Employing whatever topographical and map data that is available the PWRM user must develop a stage area table and input it to the model Typically this is done by measuring the land area encompassed by each one foot contour It is not necessary to have detailed one foot contour maps to prepare the stage area table However the accuracy of the model is directly related to the accuracy of the stage area table with flat sites being less affected than steep sites Upon input of the stage area table the model computes a companion stage storage table Special Note If the user elects to model un connected depressional storage it is modeled as an impoundment and the area at each stage below the rim elevation of the depression is not included in the stage area table However the area of the depression at or above the rim elevation is included in the table This is necessary because the PWRM computes a separate wat
9. effectiveness of the site by comparing computed retention and discharge volumes to those measured in the field using actual daily rainfall and stage data collected at the site 3 Hydrologic Setting A Introduction As shown in Figure 1 the hydrologic processes at work in either a natural or modified watershed are numerous and complex They are made even more complex by randomly varying series of rainfall events meteorological changes seasonal climatic patterns soil types topography and man made changes to the natural landscape B Soils amp Groundwater Movement Predominant soils within much of the Basin can be characterized as shallow droughty surface sands with high infiltration and lateral hydraulic conductivities underlain by a very low permeability layer of cemented silt and sand often referred to as a hardpan The depth to hardpan occurrence varies from about three feet to five feet below ground and the layer can be up to two feet thick Generally water available for vegetative uptake and evapotranspiration will occur above this layer Depressional wetlands in the locale are underlain by low permeability organic silts and clays often perching the water table Where these soils occur the predominant mode of groundwater movement 1s lateral saturated flow to lower elevation ground or to from adjacent surface water bodies However in some portions of the Basin site soils can be characterized as pervious surface beds connected t
10. 0 Number of Pumps Recorded 0 Add Modify Delete elias Basin Impoundment ON OFF Receiving Body Basin Impoundment Offsite Pump Number Mame Nominal Capacity GPM On Elevation i Feet Ort Elevation Feet Operating Time Hours Day Seasonal Operation Figure 14 Structures Pumps Enter the Nominal Capacity of the pump representing a discharge rate gallons per minute at which the pump will operate under normal conditions Normal conditions represent typical low head high volume pumps used in agricultural applications in South Florida These types of pumps will generally discharge at a fairly consistent rate operating over a small range of head The nominal capacity is a reasonable approximation of the capacity of the pump to move water Enter the operating parameters of the pump which include On and Off elevations and the anticipated operating time in hours per day Click on the appropriate button representing whether or not the pump will be operated Seasonally and then click on the ON or OFF button to have the model use this structure in the model run or not This is most useful in testing different structural and operational WMAs without having to go back and forth re entering data Page 51 Once you have entered the first pump click the Add button on the top right side of the screen The data will be saved and shown in the display box on the bottom r
11. ET evapotranspiration for short well watered grass ET evaporation from a free water surface K coefficient for short well watered grass 0 7 The value of ET is converted for other types of vegetation as follows ET ET x Ke Where K vegetation coefficient 14 Values of K are included in the model look up tables Drought Evapotranspiration Jacobs J M et al 2 noted that the methods used to predict evapotranspiration over estimate the amount during drought conditions when the vegetation 1s not benefited by an adequate water supply They partitioned ET into two stages wet and dry based on the relative position of the water table to the effective root zone and employed a reduction factor based on the vadose zone soil moisture As ranch lands within the Basin are not irrigated at all or are possibly irrigated at rates below the grass water demand a similar mechanism is included in the PWRM water balance to reduce ET during low rainfall periods Accordingly the values for drought conditions ETa can be calculated by ETa B x ET 15 Page 16 Where B reduction coefficient based on vadose zone moisture content dimensionless The reduction coefficient B 1s applied when the vadose zone soil moisture content falls below the AMC and decreases with decreasing soil moisture content SMC until the wilting point is reached Jacobs J M et al 2 found that the reduction coefficient followed a power law relations
12. TABLE LOWER UNIT HEAD CONDUCTIVITY THICKNESS MODEL COMPUTED INPUT y ZEN Mace with a Ula POTENTIAL WATER RETENTION MODEL Copy ON SMAD COMPUTATION FLOW CHART rtDraw purchased copies print this FLORIDA RANCHLANDS ENVIRONMENTAL SERVICES PROJECT as pies p OUTPUT document without a watermark LOWER AQUIFER Visit www smartdraw com or call 1 800 768 3729 Figure 2 Page 12 Since NRCS observed that runoff starts after some rain accumulates on the vegetation surfaces called the initial abstraction they modified equation 6 by subtracting the initial abstraction la from the rainfall P and added it to the potential maximum retention It 1s then rewritten as Q P Ia P Ia S where S S la 7 Accordingly equation 7 is the rainfall runoff relationship with the initial abstraction taken into account As understood by NRCS the initial abstraction consists of mainly interception by vegetation and shallow depressional surface storage all of which occur before runoff begins To remove the need to estimate these components they developed an empirical relationship between Ia and S from observation of small watersheds as la 0 2S 8 By substituting the relationship of Ia and S into equation 7 we arrive at the standard NRCS method of estimating direct runoff from rainfall as Q P 0 2S P 0 88 9 More recent work by Woodward D E et al 10 showed that the rati
13. document situations where there are multiple basins in the watershed and the basins are part of a cascading system where one basin discharges into another which discharges into another etc This allows you to enter how many basins are Upstream contributing basins that discharge into the current basin and the names of each and or how many basins and their names which the current basin discharges to Downstream which are receiving basin s There are a maximum of ten possible upstream and ten possible downstream basins that can be entered Check either the Yes or No button In this type of situation it is important to model the basins in sequence from the top of the watershed to the bottom of the watershed In more complicated watersheds it may be helpful to draw a flow diagram showing the basin inter connects so they can be entered in the correct order In this way when you go to enter this information for a specific basin the drop down box for selecting the upstream basin s will have a list of values populated with all of the previously entered basins for the user to select from The Add and Delete buttons are used to add a new connection or delete an already existing connection either upstream or downstream if it is later determined not to be accurate If you wish to add a new connection make sure to increase the number in the box above and then enter the new connecting basin and
14. for the region Water Management alternative WMA refers to the combinations of construction and management practices selected and implemented by the landowner within a defined drainage basin of the ranch in order to produce the water management services Page 3 The technical methods employed by the model to calculate the various hydrologic components are based on empirical equations and data already well documented in literature and widely used for hydrologic analysis by State and Federal agencies and private practitioners in Florida It is not the intent of the model to introduce new or untested hydrologic algorithms or to expand the current knowledge base of how the hydrologic system functions in the Northern Everglades Basin Further no attempt has been made to generalize the model for use outside of the Northern Everglades As such it employs algorithms and data already used by the South Florida Water Management District 7 Florida Department of Environmental Protection 7 the Natural Resources Conservation Service 1 4 and in extensive field level studies conducted within the Basin such as work done by Capece et al 3 While the use of empirical formulas is very well accepted and adaptable to a spreadsheet based model they are simply estimates of a much more complicated process Accordingly the model parameters and coefficients have been fine tuned during the calibration and verification process benchmarking by comparing
15. macro commands In this Section of the Manual the architecture of each module is discussed A I O Module The I O module contains all data input screens necessary to set up the model The screens are shown in Section 6 part E below The screens allow the model user to enter data for basic site information control structures pumps irrigation inputs like flowing wells onsite ditches above ground impoundments wetland area land uses topographic contours external stages if needed and inflows from upstream basins if needed When calculations are complete the PWRM creates output graphs of the various hydrologic components on a monthly or annual time step The average annual retention over the period of record is also calculated Page 22 PWRM COMPONENTS FLOWCHART Water Balance Look Up Tables Model e Conductivity e Hydrographs e Soil Storage e Storage Calcs e Runoff e Retention e Rainfall Data e Probability Reports B Water Balance Computations This section of the model computes daily water balances for three components surface water stored on site onsite vegetated area including groundwater storage and above ground impoundments C Look up Tables The following information is embedded in the look up tables l Soil types hydraulic conductivity and field capacity for all counties within the Northern Everglades Basin 4 The soil parameters are weight averaged over the reported strata 2 D
16. or Impoundment Note that even if the culvert discharges to another basin in the project the model considers that to be Offsite for calculation purposes Click either Page 48 14 the ON or OFF button to have the model use this structure in the model run or not This is most useful in testing different structural and operational WMAs without having to go back and forth re entering data Once you have entered the first culvert click the Add button on the top right side of the screen The data will be saved and the form cleared for the next culvert If you are editing a basin previously entered or need to change any data just entered select the culvert you want to modify from the Culvert Number Name drop down list and then use the same processes previously described to Modify or Delete Click on the next tab to move to the next structure type Structures Weirs Figure 13 This is the thirteenth tab from the left of the row of tabs in the upper middle section of the main screen The Structures tab opens a sub menu set of four tabs representing each of the available structure types The third type is Weirs and allows a maximum of ten weirs to be entered Select the number of weirs you want to enter from the drop down list For each weir click on the button representing where the weir discharges from then enter a Weir Number Name identifying it It 1s recommended the weirs be gi
17. the next screen while also updating all calculations and data If the user chooses to move to the next screen by clicking on that screen s tab across the middle the same calculations and data updating will occur The user is cautioned that in some cases this may take a few minutes depending on system hardware and software When entering data into the screens numerical elevation and acreage data should be entered to two decimals consistently throughout the screens There are numerous data checks made during the calculation processes that look for inconsistencies between values For example the sum of the acres of the individual soil types must be the same as the basin acres The sum of the individual land use types must also be the same as the Page 27 basin acres Minimum and maximum elevation data directly entered or calculated should be the same throughout These discrepancies may cause the model calculations to fail The user will not be allowed to continue until any discrepancies are resolved 1 PROJECT DATA Figure 1 The project data at the top of the main screen starts with selecting one item from each of the three groups on the left side of the screen gt WMA The model has to be run twice for each basin Select either Pre WMA or Post WMA depending on which model run you want to enter or modify If this is a new project you must enter the Pre WMA first gt Project Select either New or Exis
18. the pasture area The Impoundment area will also show up if it has been entered As each landuse type is added it will be listed in the box on the right side of the screen The text fields below this box are informational and will show the Basin Area entered on the main screen and then a running total of the acreages of the landuse types entered so far If you attempt to add more landuse types than the number entered or have not entered as many types as indicated or you have entered acreages that total more or less than the basin area you will be prompted to correct the data If you are editing a basin previously entered or need to edit data just entered select the landuse you want to edit from the drop down list of values and use the same processes described above for the Add Modify and Delete buttons Click on the Continue button or the next tab to move to the next screen Basin Stage Area Figure 6 This is the sixth tab from the left of the row of tabs in the upper middle section of the main screen After you have entered the Ditch Storage and Landuse data the minimum and maximum elevations will show up in the box on the left side of the screen along with instructions on modifying them if necessary They can not be modified directly in this screen This stage area input screen is for the Basin only and should not include the Impoundment if there is one That data is entered separately in the next screen You do not
19. will already be populated with the value entered on the main screen The Initial Depth to Water Table simply provides the model with a starting point for calculations If you are unsure then either estimate it or enter zero The Maximum Basin Elevation represents the highest point in the basin and is typically somewhere around the perimeter of the basin The Basin Overflow Elevation represents the highest elevation also typically somewhere around the perimeter of the basin at which any additional water would discharge uncontrolled out of the basin The Maximum Basin Elevation can be higher than the Basin Overflow Elevation The reason for entering the Maximum Basin Elevation is so that the model can include area and storage above the Basin Overflow Elevation Then if the selected WMA is to raise the perimeter berm and thus the Basin Overflow Elevation the area and storage calculations are already in place to make the estimation of increased retention The Additional Data Input box at the bottom left of the screen allows you to check off any input data that has been entered in the Client Data workbook described in Section D above When the model first opens the data from each of the input worksheets in Page 30 the Client Data workbook is automatically brought into the model workbook however the model will only use whatever data you have selected from these buttons The two boxes on the right side of the screen are for informational purposes to
20. Acres Pewa PostiwhM A Save Proweet Basin Bazin Area Acres Run the Model C New f Existing County Watershed Area Acres e alli Basin Humber of Basing E New f Existing Copy Pre to Post wih Switch between Pre 4 Past Eee Basin Soils Ditch Storage Impoundment Landuse Basin Stage Area Imp Stage Area Trend Analysis Horizontal Seepage ertical Seepage Stri gt Interface Type l Mas Distance to Surface ee Water Conveyance Feet 3 IMPOUNDMENT Length of Interface Feet PASTURE i ry Tailwater Elevation Feet en K INTERNET ie Depth to Hardpan Feet PO PASTURE PASTURE 1 Pasture Ditch 4 Pasture Offsite Ditch Add Modify Delete 2 Pasture impoundment 5 Ditch Offsite Ditch 3 Ditch Impoundment 6 mpoundment Offsite Ditch Continue Figure 9 Horizontal Seepage The first three types are internal seepage components that do not move water out of or into the basin but merely transport it from one component of the basin water table surface water or impoundment to another Each day the model uses the calculated water table elevation surface water elevation and impoundment water elevation to determine the magnitude and direction of seepage for each of the interfaces entered A positive number indicates the seepage is in the direction that the interface name assumes A negative calculation means it is moving in the opp
21. C New C Existing County Watershed Area Acres Pe Basin Number of Basins Cancel E New f Existing i Basin Soils Ditch Storage Impoundment Landuse Basin Stage Area Imp Stage Area Trend Analysis Horizontal Seepage Yertical Seepage Stri Number of Storage Ditches Ditch Humber Name Top Width Feet Side Slope Feet Ditch Depth Feet Ditch Length Feet Top of Bank Elevation Add Modify Delete Number of Ditches previously recorded Continue Figure 3 Ditch Storage Data Page 33 Once information on all of the existing ditches is collected as described in Section 6 Part B above the ditches should be grouped together if there are more than ten to be entered It is recommended that the ditches be grouped based on top of bank elevation depth and width In simple cases only one or two storage ditch groups may be sufficient to reasonably account for the area and storage while more complex systems may require all ten available storage ditches It is recommended that each ditch be given a name that is meaningful to the user for future review of the input data for instance primary secondary lateral or by top of bank elevation top width and depth The data entered for each ditch should represent an average of that ditch or the group of ditches it represents The required data elements are self explanatory and as each ditch is entered and you c
22. There are two different potential vertical seepage interface types included in the model calculations They are identified on the bottom right of the screen as Page 44 Basin to Aquifer gt l gt 2 Impoundment to Aquifer The required data elements are gt Vertical Conductivity is the rate at which the aquitard will pass water gt Head is the difference between the top of the water table elevation and the top of the underlying aquifer water elevation gt Aquitard thickness is the thickness of the semi confining layer between As discussed in Section 6 Part B 5 above it is unlikely that the required data will be readily available If the user can locate aquifer performance test data from anywhere in the surrounding area this could be used for estimating the required data Otherwise the user will need to make estimations based on best professional Data Input Florida Ranchlands Environmental Services Program Clear Current Project FRESP PROJECT DATA Ve Ma Project Service Area Acres E Pewa C PostwhA i AE See Project Basin Basin Area Acres Run the Model New i Existing County Watershed Area Acres Results Basin Humber of Basing C New f Existing Copy Pre to Post Wha Switch between Pre Post Eee Basin Soils Ditch Storage Impoundment Landuse Basin Stage Area Imp Stage Area Trend Analysis Horizontal Seepage Yertical Seepage Str Interface Type
23. User Manual for the Potential Water Retention Model PWRM The model used by the SFWMD in the Northern Everglades Payment for Environmental Services NE PES Program to estimate average annual water retention over a 10 year period of record South Florida Water Management District June 14 2012 Page 1 TABLE OF CONTENTS Section 1 Introduction and Objectives 2 Model Scope and Purpose 3 Hydrologic Setting 4 Technical Basis 5 Model Architecture 6 Data Input Requirements 7 References Page 2 Page 22 24 54 Northern Everglades Payment for Environmental Services Program User Manual for the Potential Water Retention Model PWRM for On Ranch Water Management Alternatives in the Northern Everglades 1 Introduction and Objectives The Florida Ranchlands Environmental Services Project FRESP collaboration partners developed the non proprietary spreadsheet based model described in this manual developed the non proprietary model described in this manual The model will be the common basis for the SFWMD and eligible landowners submitting a proposal to the NE PES program to predict the potential retention of on site stormwater and water pumped from offsite attributable to the installation and operation of site specific Water Management Alternatives WMAs on Northern Everglades ranchlands This Potential Water Retention Model PWRM will e Predict the daily water retained in the surface and soil profile in t
24. ailwater elevation data will be used for all of the open channels entered The Longitudinal Slope is not readily measurable in the field but can be reasonably estimated to follow the local land surface slope The Manning s Coefficient or roughness coefficient is dependent on the bottom surface of the channel and there is a list of values available Select the type of channel bottom surface based on the list and the associated coefficient will be entered into the model The Receiving Body is selected from the list of values and there are only two choices Offsite or Impoundment Note that even if the channel discharges to another basin in the project the model considers that to be Offsite for calculation purposes Click either the ON or OFF button to have the model use this structure in the model run or not This is most useful in testing different structural and operational WMAs without having to go back and forth re entering data Once you have entered the first channel click the Add button above the display window on the right side of the screen The channel you entered will show up in the display window and you can proceed to enter more channels if necessary If you are editing a basin previously entered or need to change any data just entered select the channel you want to modify from the Channel Number Name drop down and then use the same processes previously described to Modify or
25. aily rainfall record from 1930 through 2011 from the SFWMD Okeechobee Field Station 3 Monthly evaporation data 6 Page 23 6 Data Input Requirements A Basin Boundaries Before inputting any data to the PWRM the user must study the site and conduct field observations to clearly define the site drainage divides and the total area of the site This is a one basin model As such it is not equipped to compute offsite sheet flow from adjacent upstream basins If there are offsite inflows they must be represented as daily inflows computed from previous model runs or other records B Existing Physical Features l Onsite Ditches Catalog all existing onsite ditches including length bottom elevation and cross section This is input to the model to create a portion of the stage storage and stage area curves Supplemental Water Sources Identify onsite flowing wells and compile a daily flow volume gallons for the period of record being modeled and include this as a Flowing Wells input file to the model If there are pumped wells and or surface water pumps used to import water for irrigation include a similar daily flow volume Irrigation input file Control Structures Identify and obtain dimensions and elevations of all culverts pumps ditches and flashboard risers that control discharge from the site If the user wants the model to check for submerged or reverse flow of gravity controls downstream daily elevations or a
26. be used as it is a quantifiable distance from the edge of water in the impoundment to the Page 18 edge of water in the ditch In the cases of seepage to or from a surface water source to vegetated areas the PWRM is not able to understand the geometry of the site so L is estimated by the user based on average site conditions L Vertical Ground Water Seepage If the user believes that the site lithology supports inclusion of a vertical seepage component it can be turned on in the input screen As discussed in the previous section regarding the hydrologic setting of the modeled area it is assumed that the water table aquifer 1s separated from the lower aquifer by a lower permeability aquitard Vertical seepage 1s estimated using the Darcy velocity equation 20 with a reasonable estimate of the aquitard hydraulic conductivity provided by the user In this case H H2 is now the elevation difference between the two aquifers and L is now the vertical thickness of the aquitard The user must provide an estimate of H H2 VSP is then computed by multiplying the Darcy velocity by the site area In the real physical system the vertical seepage into the aquifer below the water table could be expressed as recharge to downstream surface waters However the fate of vertically seeped water is beyond the scope of the PWRM It is considered a site water retention as the water is not directly discharged to surface waters adjacent to the modeled site
27. ces Program Clear Current Project FRESP PROJECT DATA iM Project Service Area Acres Za C Pre WMA C PosttwMa Project C New Basin i New Basin Basin 4rea Acres C Existing County Watershed Area Acres eee Number of Basins C Existing Copy Pre to Post WMA Switch between Pre Post Close Basin Soils Ditch Storage Impoundment Landuse Basin Stage Area Imp Stage Area Trend Analysis Horizontal Seepage Yertical Seepage Stri Define Stage Area Range m Elevation Input Elevation Area Feet Acres ei per Elevation Minimum Elevation iz Maximum Elevation 1 5 To modity the Minimum or Masirium Elevation Change the Maximum Elevation Add andor lmpoundment Depth on the Impoundment Form Modify Continue Figure 7 Impoundment Stage Area The center box on the screen is for Elevation and Area Input The area at the minimum and maximum elevations will already be shown in the display box You will need to enter the area for each elevation between the minimum and maximum by entering the first elevation and area in the boxes on the left and hitting the Add button This data in the display box will be updated with the new information Continue until you have entered everything you need to up to the maximum elevation and area Page 39 If you are editing data for an impoundment previously entered or need to change any data just e
28. constant tailwater elevation must be provided Ditches Adjacent to Site If there ditches or surface water features adjacent to the site that could receive lateral seepage compute the length of the feature adjacent to the site and obtain estimates of the seasonal water elevation While the elevation data is input on a daily basis daily values are often not available Accordingly the user will have to estimate the values based on field reconnaissance and knowledge of the area As seepage to an external adjacent ditch is much greater when it is adjacent to an internal above ground impoundment separate the length of ditches adjacent to the impoundments from the rest of the site Vertical Seepage If the user believes there 1s vertical seepage obtain representative hydraulic conductivity data for the aquitard and lower aquifer potentiometric water elevation While the potentiometric data is input on a daily basis it is most likely the data won t be available which requires the user to make estimates based on expected seasonal variations Wetlands and other Depressions Using aerials or survey data estimate the surface and bottom area of wetlands and other depressions The maximum depth of these features must be estimated based on survey or field approximation This is input to the model to create a portion of the stage storage stage area curve Page 24 7 Topographic Contours Topographic contours are used to compute the surface area with
29. creages that total more or less than the basin area you will be prompted to correct the data Data Input Florida Ranchlands Environmental Services Program Clear Current Project FRESP PROJECT DATA WMA Project Serice Area Acres C PrewMa PostiwMA i a i Pree Bazin i Basin Area Acres urethe He C Hew Existing County Watershed 4rea Acres eer Basin Number of Basins i New i Existing Copy Pre to Post Wiha Switch between Pre Post Ene Basin Soils Ditch Storage Impoundment Landuse Basin Stage Area Imp Stage Area Trend Analysis Horizontal Seepage Yertical Seepage Stri Soil Types Number of Soil Types Soil Types kd Acres Add Modify Delete Total Basin Acreage Total Soil Acreage Continue Figure 2 Soils Data If you need to change the acreage of a soil type already entered select that soil type from the box on the right The soil type and acres will show up in the boxes on the left and you can edit the acres then click the Modify button If you need to increase the number of soil types then change the number of soil types and proceed to Add the new soil type s If you want to decrease the number of soil types and you have already entered acreages for the number of soil types previously entered then first select the soil type you want to delete from the box on the right side of the screen and click the Delete button T
30. d Station are embedded in the model in inches of rainfall The period of record is from January 1 1999 to December 31 2008 The user can view the data set in the look up tables section of the PWRM Longer periods of record can be used but become computationally burdensome to typical desktop computers If the user wishes to evaluate a site using a longer period of record it 1s suggested that rainfall data be input in ten year increments running the model as many times as needed to cover the desired period of record If the user has site specific daily rainfall records they can be substituted for the SFWMD data in the look up tables However the data set has to be continuous for the same ten year period of record E Surface Runoff From Vegetated Surfaces Incoming rainfall will contribute directly to surface storage infiltrate to become soil storage or run off After studying the runoff from gauged watersheds in response to rainfall the SCS now NRCS 1 observed that the ratio of actual rainfall retention in a watershed to the potential maximum retention 1s equal to the ratio of the actual runoff to the potential maximum runoff In formula terms F Q Where F actual retention 4 S P S potential maximum retention S gt F Q actual runoff P potential maximum runoff P gt Q Further F P Q 5 Equation 4 is rewritten and solved for Q as Q P P S 6 Page 11 STAGE AREA CURVE DAILY RAINFALL
31. e breakpoint as the maximum elevation You will also see the data that has been previously Saved for this basin so that you can compare the results of any changes you make If this is a new project the Saved data will reflect null values or zeros The Current data will reflect either what is Saved or whatever values you are currently testing The Equation and R Squared text boxes below the graph are for informational purposes and can not be directly modified The R Squared value may be a useful indicator of how well the trend line fits the dataset You have the option to try any of the equation types Linear Polynomial 2 Order or Polynomial 3 Order by selecting from the Trendline Type drop Page 41 10 down box in the Current data section on the bottom left side of the screen to see 1f any of them fit the dataset fairly well or if it should be broken up If you want to use the single equation do not add a breakpoint The model will store the type of equation and the coefficients of that one equation and use it for calculations from the minimum to the maximum elevation for the Storage Stage relationship The user is cautioned that 2 and 3 order polynomials can produce unexpected results in some cases so it is important to carefully review the output data for outliers To break up the equation select the first breakpoint elevation from the Elevations drop down box in
32. e cover Capece 3 and others have therefore replaced the initial abstraction term in the NRCS runoff equation with available soil storage and estimate the runoff curve number as a function of available soil storage In South Florida this seems to provide adequate estimates of runoff with a better fit of observed and computed values at higher rainfall amounts E Evapotranspiration Pasture grasses dominate the vegetation found in the Basin s ranchlands Mixed in with the pastures are native wetlands both herbaceous and forested and upland forests Occasionally one will find other agronomic activities within the site including citrus and vegetable production From a water balance perspective the type of vegetative cover affects ET due to variations in the seasonal growing cycle texture of the vegetated surface percent of ground cover and effective root zone Seasonal climatic variations of temperature cloud clover precipitation wind speed and direction foliage cover incoming solar radiation albedo and humidity have a direct impact on evapotranspiration These variations occur continuously during the day but have statistically documented seasonal trends According to the literature ET 1s greatest from an open water surface 5 6 As direct ET measurements are only performed in a research setting ET for specific agricultural production sites is estimated by various ET formulas This is typically done in Florida by application of model
33. e surface area computed by the stage area curve and from the impoundment based on the user supplied impoundment area The model compares the water table elevation to the onsite surface water elevation computed by the stage volume and computes lateral seepage to or from the water table by the Darcy Equation This is also done independently for the above ground impoundment If vertical seepage is included the model compares the water elevation in each of the three components to the potentiometric elevation of the lower aquifer and vertically seeps water based on the Darcy equation Based on the stage of the onsite surface water storage and discharge control devices selected by the user the model adds or deducts water from the site surface storage and the impoundment Depending on the pump and impoundment characteristics nominal pump rate on elevation maximum storage elevation size of the impoundment provided by the user water is taken from the connected surface storage to the above ground impoundment if one is included The model can also run a surface water pump that discharges directly offsite with a similar set of input specifications If a depressional impoundment is included the model continues to add rainfall seepage and runoff until the impoundment is filled to the rim elevation As long as the water level is at the rim elevation further rainfall seepage and runoff is returned to the connected surface storage as it can no longe
34. ed 0 Add Modify Delete Source Basin Tmpoundment Upstream Invert Elevation i Feet Culvert Number Downstream Invert Elevation Mame i Feet Material Manning s Coefficient Geometry m Discharge Coefficient View Tlustration Diameter Inches 4 Entrance Loss Coefficient Height Inches Tailwater Elevation i Feet Width t Inches 3 Receiving Body Length i Feet Culvert Figure 12 Structures Culverts Select the culvert Geometry from the list of values Depending on the geometry you select enter the Diameter Height and Width as appropriate Enter the Length of the culvert and the Upstream and Downstream Invert Elevations Select the Discharge Coefficient from the list of values accessed using the down arrow at the right end of the box You can click on the View Illustration button to the right to help you select the appropriate coefficient You must either enter a Tailwater Elevation based on in field analysis landowner input etc that will be used as a constant for every daily calculation or provide an Input file in the Client Data workbook Client Tailwater Data worksheet However if you do not enter a tailwater elevation for each culvert the same tailwater elevation data input file will be used for each of the culverts entered without a specified tailwater elevation The Receiving Body is selected from the list of values The choices are Offsite
35. ed If you are working on an existing project and basin and need to make a minor modification and re run the model then after making the changes click on Run the Model You can Save the data at any time but note that this will re calculate the entire model The Results button will copy the results to the Output Workbook discussed in Section D above Close will exit the model without saving any changes although you will be asked to confirm this If this 1s a new project and you haven t entered all of the necessary information you can still Save the data and return later to finish but the Results may not be accurate To ensure that the Results are accurate you will need to have both the Pre WMA and Post WMA data completed and saved Then run the Pre WMA model and click on the Results button and immediately after run the Post WMA model and click on the Results button If you run a different project and or basin in between the results will not be accurate Basin Figure 1 This is the first tab on the left of the row of tabs in the upper middle section of the main screen If you are working with an existing basin the information previously stored for this basin will already be populated This data can be modified as needed but be cautious about acreage and elevation changes as mentioned in the introduction to Section E above The four boxes in the top left corner start with the Basin Area which
36. elevation for ones near the top of the basin but they are all two feet deep To account for this you should enter the highest top of bank elevation and a depth that will result in a bottom Page 36 elevation of the lowest wetland In other words you may have to enter a grassy wetland with a depth of eight feet which is not real but allows the model to better calculate areas at each elevation to include the entire group of wetlands Enter the Number of Landuse Types maximum 6 in the box at the top left side of the screen If you have entered Storage Ditches and or an Impoundment include each as a landuse type in the number To add wetlands use the box on the left side of the screen and select a wetland type from the list of values The data required for each wetland type is self explanatory You have the option of entering either the Area at Minimum Elevation bottom area or Side Slope where the number you enter is Horizontal change per 1 foot vertical change When finished with each type click the Add button To enter uplands use the box in the center of the screen and select the upland type from the list of values The data required for each upland type is self explanatory Keep in mind that the Storage Ditch area has already been calculated and listed in the table on the right based on data previously entered Typically the ditch area would come out of the Pasture area and this should be taken into account when calculating
37. ential daily surface discharge of water from the site exceeds the amount left in the surface storage the model limits the discharge to the amount that is actually available for discharge above the control elevation e g weir crest elevation 2 Ifthe daily potential pumpage to an above ground impoundment exceeds the amount left in the surface storage available for pumping the pumpage is set to the amount that 1s actually available above the pump shut off elevation 3 If the daily rainfall is less than the initial abstraction all of the rainfall is infiltrated into the vegetated surface 4 The model tests to determine where the water table is relative to the effective root zone and computes ET and vadose phreatic zone additions deletions accordingly 5 If downstream stages are provided by the user the model tests to determine if submerged weir flow exists or if there is flow reversal back into the site 6 If onsite surface storage stages exceed the basin boundary elevation the model computes the volume of water above the boundary elevation and deletes it from the onsite surface storage 5 Model Architecture The formulas and data discussed in previous sections were placed into Microsoft Excel spreadsheets As shown in the following graphic the spreadsheets are organized into four main sections 1 the I O module 2 water balance computations 3 look up tables and 4 reports Data are exchanged between sections using cell references and
38. er balance for the un connected depressional storage until the depression is filled to the rim elevation When the depression is filled to the rim elevation the storage above that elevation 1s considered to be hydraulically connected and is accounted for in the stage area and stage storage tables As direct reference to the stage area and stage storage tables is computationally cumbersome for the model the tables are approximated through a curve fitting technique so that an equation can be used in the daily calculations to describe the stage area and stage storage relationships Upon input of the tables the PWRM plots the data and prompts the user to select a curve type polynomial or linear that best fits the data Water Balances The PWRM computes water balances on a daily basis for various inputs outputs and storage components Separate water balances are performed for vegetated surfaces and for those that are under water inundated This is shown graphically in Figure 2 and the computational procedure is discussed in the later paragraphs For vegetated surfaces the daily change in soil storage AS from the water balance can be presented as follows AS P R ET HSP VSP 1 Page 9 Where AS change in soil water storage P precipitation R Surface Runoff to onsite connected storage or to depressional impoundment ET evapotranspiration from vegetated surface HSP and VSP horizontal and vertical seepage seepage into the
39. er table is depressed below the effective root zone might not provide enough infiltration to raise the water table but they will replenish the SMC in the effective root zone Therefore the SMC is adjusted based on these additions commensurately increasing the ETa These conditions are best shown by formula for each condition Condition 1 Water Table at or Within Effective Root Zone ET ET 17 Condition 2 Water Table Below Effective Root Zone ET ETa and 18 SMCn SMC ET gn 1 VIN 19 Page 17 Equation 19 is controlled by a logic test that will not allow the vadose infiltration VI to increase the SMC above the available moisture capacity AMC When there is excess TI the SMC is set equal to the AMC and the remainder of the TI is added to the phreatic zone Irrigation Where pastures are irrigated irrigation 1s usually accomplished through a network of widely spaced ditches and shallow swales The net effect of irrigation is to add water to the onsite surface storage followed by horizontal seepage into the ground water table Accordingly on ranches where irrigation is practiced or proposed as a WMA the PWRM water balance adds irrigated water to the surface storage volume Horizontal seepage is estimated with the Darcy equation linking the surface storage and vegetated surface components discussed earlier Daily irrigation volumes from onsite wells are input by the user based on irrigation records or through some prop
40. esses The Client Data workbook consists of eleven worksheets The first worksheet Client Project Info is not intended to be modified by the user This worksheet is directly populated and updated by the model data input menu system The other worksheets in this workbook are where additional data that the user may need to provide to the model 1s stored This includes things like culvert tailwater evaporation offsite inflows flowing wells irrigation tailwater recovery offsite seepage tailwater elevations and open channel tailwater elevations Additional data the user wants to provide must be in the form of two columns of data where the first column is the date and the second is the value flows in gallons per day evaporation in inches per day or elevations in feet per day The input data file must be continuous and include the exact same time period as the model start and stop dates January 1 1999 through December 31 2008 with no missing values Columns A and B in each of these sheets are used by the model to import the data Note that column A already has the dates in place for the 10 year model runs so the user will only need to copy in the data values The other pairs of columns to the right in each worksheet are for the user to store the data specific to each project and basin Rows 1 through 3 656 are used to store the Pre WMA data and rows 3 657 through 7 312 are used to store the Post WMA data Prior to running a particu
41. f there 1s an impoundment You will need to enter the area for each elevation between the minimum and maximum by entering the first elevation and area in the boxes on the left and hitting the Add button This data in the display box will be updated with the new information Continue until you have entered everything you need to up to the maximum elevation and area If you are editing data for a basin previously entered or need to change any data just entered select the row of data you want to change by clicking the radio button next to it in the display box and that data will show up in the boxes on the left Edit the data and click the Modify button If you need to delete an entry click on the radio button next to it in the display box and hit the Delete button Click on the Continue button or the next tab to move to the next screen Page 38 8 Data Input Impoundment Stage Area Figure 7 This is the seventh tab from the left of the row of tabs in the upper middle section of the main screen After you have entered the Impoundment data the minimum and maximum elevations will show up in the box on the left side of the screen along with instructions on modifying them if necessary They can not be modified directly in this screen This stage area input screen is for the Impoundment only and should not include the Basin data That data is entered separately in the previous screen Florida Ranchlands Environmental Servi
42. g the elevation of the site boundary 8 Adding or deleting supplemental water sources and adding offsite inflows and 9 Changing crop types 10 Implementing a stormwater tailwater recovery system for supplemental irritation D Model Installation The model was developed using Microsoft Excel 2003 and has been tested in version 2007 with no documented problems as of this writing It is currently not compatible with the 2010 version A user requesting a copy of the model will receive it electronically in the 2003 version If the user has a newer version of Excel it can be opened and then saved to that version The model will be contained in a single folder that will include three workbooks a copy of the User Manual and a blank Error Log File gt The PWRM Model workbook contains the model itself gt The Client Data workbook stores the user s project data and allows the user to provide additional data to the model that is not included in the embedded lookup tables or the data input system and Page 25 gt The Output Data workbook where the model results are written and made available to the user It is recommended that the folder be copied to the user s desktop but it can be copied to another directory The original model folder provided to the user electronically should be preserved in case it becomes necessary to re load the model To simplify running the model shortcuts for each of the three workbo
43. have to enter separate stage area relationships for each landuse The data you enter here should include all wetlands uplands and ditches Page 37 Data Input Florida Ranchlands Environmental Services Program Clear Current Project FRESP PROJECT DATA iM Project Service 4rea Acres C Pewa C PostwMA ect Fi Acres Project C New Basin i New Basin r Basin 4rea Acres unethe Made C Existing County Watershed Area Acres peer Number of Basins C Existing Copy Pre to Post whl Switch between Pre Post Close Basin Soils Ditch Storage Impoundment Landuse Basin Stage Area Imp Stage Area Trend Analysis Horizontal Seepage Yertical Seepage Stri m Define Stage Area Range Elevation and Area Input Elevation Area Feet Acres oe Sree Elevation Minimum Elevation is evalgr To modify Minimum Elevation change either Area Landuge Area at Minimum Elevation Ditch Storage Ditch Depth HM axinium Elevation iz To modify Maximum Elevation change Basin Maximum Basin Elevation Continue Figure 6 Basin Stage Area The center box on the screen is for Elevation and Area Input The area at the minimum and maximum elevations will already be shown in the display box The Acres reported for the maximum elevation in the display box will reflect the total basin area if there is no impoundment or the total basin area less the impoundment area i
44. he drainage area influenced by a WMA with and without the WMA e Partition the retained water into water lost to ET and water that seeps through the subsurface e Aggregate the water retained over a water year or other time period of interest e Provide an average of the expected water retained over the water year s or other time period based on the historical rainfall record e Rely on data that is readily available or would be low in cost to obtain for a typical Florida ranch and for scoping initial WMA design and operation e Require no more than 4 weeks to apply by a mid level engineer BS with experience or MS or contractor e Be benchmarked using data streams for the eight pilot sites to provide a high degree of confidence that the resulting model can be applied to sites in the Northern Everglades e Is sufficiently documented and open access to allow model improvement over time as new data streams associated with the program s verification requirements become available 2 Model Scope and Purpose The purpose of the PWRM is to estimate the amount of rainfall and other inflows to the site that are retained as opposed to detained with and without a proposed specific WMA design and operation The estimates are made on a daily volumetric basis using historical daily rainfall events recorded within the Northern Everglades Basin other user provided daily input data sets published soil parameters and evapotranspiration ET estimates
45. hen go back and reduce the number of soil types If you want to decrease the number of soil types and you have not already entered acreages for the number of soil types previously entered then just change the number of soil types Keep in mind if you are going to increase the number of acres a particular soil type and have already entered enough acres to match the basin acreage you will first need Page 32 to reduce the acres of one or more of the other soil types already entered by the same amount using the modify procedure described above If you are modifying a basin previously entered use this same process Click on the Continue button or the next tab to move to the next screen 4 Ditch Storage Figure 3 This is the third tab from the left of the row of tabs in the upper middle section of the main screen There are a maximum number of ten Storage Ditches that can be entered for each basin The purpose is to allow you to reasonably estimate the storage area and volume that can be achieved in the ditches You can then modify the ditches in the Post WMA model to increase storage capacity if this 1s a desired WMA The model uses the information entered to calculate areas and volumes at each stage Data Input Florida Ranchlands Environmental Services Program FRESP PROJECT DATA at A Froject Service Area Acres C Prewea C Postiha i _ Proect Basin i Basin Area Acres _ Aurcthe Me
46. hip based on a measured soil moisture content ranging from field capacity to permanent wilt AMC Field capacity 1s defined as the amount of soil moisture held by soil particles after gravity drainage of the matrix has ceased The effective root zone is defined as the depth at which most of the plant roots are found As long as the water table stays below the effective root zone the plant continues to deplete the moisture held by the soil particles within the effective root zone until the moisture content is reduced to the wilting point At that point essentially no moisture is available for plant uptake and evapotranspiration minimizes Values for the AMC are available from the NRCS Soil Survey 4 For use in the PWRM the same power law relationship is used however the linear coefficient is varied depending on the soil type and depth of effective root zone as follows B KxSMC 0 0 lt B lt 1 0 16 Where K 1 AMC SMC soil water content inches with a maximum value equal to the AMC and a minimum value of zero When the water table is within the plant s effective root zone water is readily available for crop uptake and B would have a value of 1 0 The PWRM water balance checks the depth to water table on a daily basis and when it drops below the effective root zone the ET rate is adjusted downward until the permanent wilting point is reached when ET becomes zero Small rainfall events that occur while the wat
47. ight of the screen The form will be cleared for the next pump to be entered If you are editing a basin previously entered or need to change any data just entered select the pump you want to modify from the Pump Number Name drop down list and then use the same processes previously described to Modify or Delete Click on any other tab to move to a different screen F Save Run and Review Results Once you have entered the Pre WMA data click the Save button on the top right side of the main Project screen The data will be saved to your Client Data workbook Client Project Info worksheet Then click the Run the Model button to update all model calculations and results You can then use the Copy Pre to Post WMA button under the County box and then modify the necessary data for the Post WMA model In most cases you will want to use this to save time since most of the data does not change between Pre and Post conditions Alternatively you can click the Clear Current Project button and enter the Post WMA data Once this is complete click the Save button on the top right side of the main Project screen The data will be saved to your Client Data workbook Client Project Info worksheet Then click the Run the Model button to update all model calculations and results Then click the Results button to copy the model output to the Output workbook You can then close
48. in Area Acres 659 00 Run the Model C New iv Existing County Okeechobee F Watershed Area Acres 659 00 Results Basin Number of Basins 1 i New f Existing Copy Pre to Post WMA Switch between Pre Post Eas Basin Soils Ditch Storage Impoundment Landuse Basin Stage Area Imp Stage Area Trend Analysis Horizontal Seepage Yertical Seepage Stri f Basin C impoundment First Equation Second Equation Third Equation Select Data to Analyze Storage Stage Basin Storage Stage Select Equation 3rd Equation C ist t 2nd 3rd 445 39 5 34 5 295 a34f 334 2 aad BAAT Aaa ye DaF Storage ac ft Saved ist 2nd Breakpoints ae Be Trendline Polynomial 2nd Order Type Elevation ft Current ist ond Breakpoints 29 5 30 5 Elevations Trendli tie ne Polynomial 2nd Orde Update Flot a i a Equation a veh je R Squared 9995 Figure 8 Trend Analysis Given Stage Poly Given Stage The Trend Analysis screen will start with the Basin radio button selected and the Storage Stage relationship in the Select Data to Analyze drop down box In the Select Equation box the radio button next to 1 will be selected and the graph in the display box will show the entire dataset from the minimum elevation to the maximum elevation If this is an existing project and basin that already has a breakpoint s the graph will reflect th
49. in each contour interval This data is input to develop stage storage and stage area curves for storage above the onsite ditches and depressional areas up to the elevation of the site boundary While one foot contours are preferable the user is able to use whatever topographic information that is available to estimate the surface area at one foot elevation intervals 8 Soils Using NRCS soils maps compute the surface area of each soil type 9 Land Uses Using aerial photographs confirmed by field observation input the surface area of each land use including pasture upland forest herbaceous wetlands forested wetland citrus groves and vegetable fields C Proposed Water Management Alternatives Select potential water management alternatives WMAs for analysis and comparison to existing site conditions Some examples of WMAs include but are not limited to l Replacing uncontrolled open ditch and culvert discharges with flashboard risers weirs or pumps 2 Changing the size and or elevation of existing culverts and flashboard risers seasonal flashboard elevation settings are possible 3 Adding bleeder notches to flashboard risers 4 Adding or modifying existing above ground impoundment with pumps and control structures 5 Increasing storage by adding a depressional impoundment or isolating a previously connected wetland 6 Adding ditches at site boundary to enhance lateral seepage offsite 7 Increasing storage by raisin
50. ion Another example would be in how runoff from vegetated surfaces to surface waters is computed The NRCS equation simply computes runoff based on the daily computed depth to root zone averaged over the entire vegetated area a weight averaged specific capacity units of water per unit of soil and the daily rainfall This is consistent with the NRCS s development of the runoff formula and assumes all computed runoff contributes to increased surface storage no matter how far the water would actually have to travel to get there Input features have been included to define the type and size of drainage control features such as weirs open ditches pumps and culverts If the information is available the user can also input daily flow and stage data for offsite receiving bodies such as ditches that are adjacent to the site Input screens are also provided to describe above ground impoundments surface water pumps and flowing wells Page 4 There are two modes in which the model can be used The first mode calculates the runoff retention volumes for use in analyzing the potential water retention of a candidate NE PES program site and various proposed water management alternatives WMAs using the historic rainfall and ET data records This gives the participants an opportunity to evaluate the cost and benefit of the WMAs prior to implementation Once a candidate WMA site is selected and implemented the model can be used in another mode to monitor the
51. itional models like Blaney Criddle it requires the input of several climatic parameters including net incoming solar radiation air temperature wind speed and relative humidity These parameters are not usually collected at individual ranches or the period of record of these observations at local weather stations is very short less than 10 years Jones J W et al 6 computed E rates with the Penman equation on a monthly basis for average meteorological conditions in various parts of the State from meteorological observations available at that time The South Florida Water Management District has accumulated up to six years of daily Eo data at a few sites in the Northern Everglades and computed E with the Simple Abtew Equation Abtew W 11 The data is available on the SFWMD s DBHYDRO data base Since the PWRM will be used to evaluate potential sites over a period of record of 10 years or greater the average E data presented by Jones et al 6 1s currently being used These average rates are provided in the model from a look up table Daily values are computed by dividing the monthly data by the number of days in the month The user should note that the average E values are not correlated to actual meteorological conditions at any particular site Rainfall is typically associated with cloud cover which reduces net radiation increases relative humidity and changes the Page 15 wind speed all of which affect E Accordingly
52. land surface that is not under water 2 connected surface water storage connected by ditches to the site discharge points and 3 un connected impoundments no ditch connection Un connected surface storage can consist of either pumped above ground impoundments or below ground storage in wetlands or lakes which are isolated from the site s discharge points On a daily basis the model computes how much of site is under water the connected surface water storage and how much is not This is determined by the stage area relationships provided by the user If an impoundment is present the area of the impoundment is included in the total site area but the stage storage curve for the connected surface water storage does not include the storage associated with the impoundment this is explained further in the following paragraphs The three components are linked to each other through empirical formulas describing conveyance mechanisms such as seepage runoff and pumping B Stage Storage and Stage Area Curves The basic ranch site usually includes upland pasture and native areas wetlands and ponds that have been hydraulically connected by ditches one or more surface discharge points Page 8 and ditches that hydraulically connect these features It is recognized that there can be significant depressional storage features like wetlands or lakes which are not directly connected to the onsite ditch system and discharge points When these un connected
53. lar project and basin the user can go into the appropriate worksheet s and copy the data values from the stored data area to column B Save the Client Data workbook and close it before opening the model Page 26 The Output Data workbook consists of four worksheets and the user is cautioned not to change or rename these worksheets The first three worksheets each include both the Pre WMA results in rows 1 through 3 999 and the Post WMA results in rows 4 000 through 7 999 The first worksheet is the Discharge Compiler which includes daily calculations for separating discharge out based on the source and receiving body of each discharge structure This is useful when the user needs to split the discharge in order to route it to a different basin by entering it into that basin model s input worksheet The second worksheet is the Output which includes the entire daily calculation section of the model The third worksheet is the Results which include monthly and annual roll up summaries of the daily data The fourth worksheet is Graphs and includes the automatically generated graphic output showing both Pre WMA and Post WMA retention and discharge results This workbook can be used to review analyze manipulate and or print the data or graphs The user is cautioned that the worksheets in this workbook will be overwritten the next time the model is run so it is recommended to save this o
54. lick the Add button they will appear in the box on the right side of the screen along with a running count of the number of ditches entered so far in the box below Modifying and or deleting a ditch is accomplished by selecting one previously entered from the Ditch Number Name drop down box Then change whatever data you need to change and click the Modify button or just click the Delete button if you need to delete it If this is an existing basin the data previously entered will already be displayed and can be modified in the same way described above The only restrictions are a maximum of ten ditches and whatever number of ditches you entered in the box on the top left side of the screen the same number of ditches must be entered before clicking on the Continue button If you originally entered three ditches and need to add more change the number before adding any If you originally entered three ditches and need less use the Delete function described above The number of ditches will automatically adjust downward as you delete If you are modifying a basin previously entered use the same process Click on the Continue button or the next tab to move to the next screen Impoundment Figure 4 This is the fourth tab from the left of the row of tabs in the upper middle section of the main screen Only one impoundment can be entered for a single basin If there is or it is proposed to have more than one
55. more accurately the amount of available soil storage above the water table best matched the field data Capece J C et al 3 concluded that use of the soil storage capacity curve developed by the Agricultural Research Service ARS best fit the observed runoff data Page 13 The author compared the ARS curve 3 to the available moisture capacity AMC data found in the NRCS Soil Survey 4 for Myakka soils and found the values to be quite similar AMC is expressed as the volume of water in inches stored per unit depth of soil Accordingly it should be appropriate to use published AMC data 4 for the purpose of estimating the value of S and consequently the curve number CN for each soil series represented on the site Accordingly S is computed by S DWT AMC 11 Where DWT depth to water table feet AMC available soil moisture capacity from NRCS Soil Survey weight averaged over the surficial soil strata presented in the Soil Survey inches of water per inch of soil It is interesting to note that although both the ARS 3 and SFWMD 7 values are numerically similar to the NRCS AMC values the NRCS defines the AMC as the difference between field capacity the maximum amount of water held that can be held in the soil pores after gravity drainage is complete and the amount of moisture at the vegetation wilting point Intuition would lead the practitioner to use higher values closer to the soil porosity in equation 11 not
56. nca ne Mas Water Elevation Feet Side Slope H 1 Mas Impoundment l Depth Feet Elevation impoundment Overflow Elevation Add Modify Delete Continue Figure 4 Impoundment The pump station s that add water to the impoundment and the control structure s that discharge from the impoundment are entered in the Structures screens at the end of the menu system These will include the necessary physical parameters and operating conditions to allow the model to move water back and forth between the basin and the impoundment and or offsite depending on the prescribed conditions If you are modifying an impoundment previously entered change the data and click Modify If you want to delete an existing impoundment click Delete Click on the Continue button or the next tab to move to the next screen Page 35 6 Data Input Landuse Figure 5 This is the fifth tab from the left of the row of tabs in the upper middle section of the main screen The Landuse screen is divided into two groups Wetlands and Uplands Within the wetlands group are Grassy Wetlands and Forested Wetlands Within the uplands group are Pasture Grass Forested Uplands Citrus and Vegetables The Storage Ditch and Impoundment data if applicable should have already been entered and will automatically show up in the box on the right side of the screen Florida Ranchlands Environmental Services Program Clear Curre
57. nt Project FRESP PROJECT DATA iM Project Service 4rea Acres C Pewa C PostwMaA ect Zi Acres Project i New Basin C New Bazin r Basin Area Acres i ably Existing County Watershed Area Acres eel Number of Basins Existing Copy Pre to Post WMA Switch between Pre Post coe Basin Soils Ditch Storage Impoundment Landuse Basin Stage Area Imp Stage Area Trend Analysis Horizontal Seepage Yertical Seepage Stri Number of Landuse Types Landuse Wetlands Uplands Wetland Type ha Upland Type siete Lie et Sea Area at Maximum Elevation Acres Maximum Wetland Elevation Feet Maximum Depth Feet Area at Minimum Elevation Acres Minimum Elevation Feet Area at Minimum Elevation Acres OF Slope H 1 Add Modify Delete Add Modity Delete Total Basin Acreage Total Landuse Acreage Continue Figure 5 Landuse Each landuse type is entered only once so the required data must be averaged and adjusted as necessary to allow the model to reasonably estimate the area of that landuse type for each topographic stage elevation For example if you have ten different grassy wetlands in the basin they are probably all about two feet deep If the basin has some topographic fall across it the top of bank elevation for wetlands near the bottom of the basin may be several feet below the top of bank
58. ntered select the data you want to change by clicking the radio button next to it in the display box and that data will show up in the boxes on the left Edit the data and click the Modify button If you need to delete an entry click on the radio button next to it in the display box and hit the Delete button Click on the Continue button or the next tab to move to the next screen Trend Analysis Figure 8 This is the eighth tab from the left of the row of tabs in the upper middle section of the main screen Once the stage area data for the basin and impoundment have been entered the model requires equations that will reasonably estimate the following relationships for each one set for the basin and one set for the impoundment gt Given a storage volume calculate a stage gt Given a stage calculate an area gt Given a stage calculate a storage volume The model uses the Trend Analysis function of Excel to generate equations to represent each data set The type of equation linear 2 order polynomial or 3 order polynomial and the coefficients for each term of the equation are stored and the model uses this information to calculate the necessary daily relationships The difficulty is that each of the relationships is generally not represented very well by a single equation due to the differences in landuse A typical ranch in the Northern Everglades Basin includes some ditch networks a lot of improved pa
59. o a lower elevation aquifer by semi impervious layers called aquitards These soils will exhibit both horizontal seepage and vertical seepage to from the lower aquifer Typically one would observe a water table aquifer and a semi confined aquifer below the aquitard Vertical seepage rates are controlled by the conductivity of the aquitard and the relative potentiometric elevation of the two aquifers While lateral flow in the lower semi confined aquifer can transport water to down stream surface features this process is not usually well defined and is beyond the scope of the PWRM Accordingly the model reports vertical seepage as retained water in that it doesn t directly contribute to surface water discharge at the site boundary The user is cautioned to carefully evaluate the site soil conditions to determine if it is appropriate to include a vertical seepage component in a model run C Rainfall The Northern Everglades Watershed experiences large amounts of precipitation Typically the majority of the rain falls in the summer months from June to October The Page 5 Basin also experiences extended periods of very low rainfall sometimes lasting over a month The spatial and daily distribution of rainfall 1s quite varied and the response of the land to a particular rainfall event is never quite the same However when evaluating the potential of a particular site to retain water before and after implementation of WMAs use of historic dail
60. o of initial abstraction to maximum potential retention 1 S originally assumed by the NRCS ratio of 0 2 is incorrect and proposed a ratio of 0 05 Use of the 0 05 ratio proved to provide much better correlations of measured vs modeled discharges Accordingly equation 9 was modified to Q P 0 05S 7 P 0 95S 10 NRCS noted that the amount of available soil water storage capacity can change when there are successive storm events of sufficient magnitude and frequency that the soil storage cannot fully recover prior to the next storm The NRCS attempted to account for this by creating three antecedent moisture conditions that would modify the value of S also expressed as the curve number CN where CN 1000 S 10 Capece J C et al 3 reviewed rainfall runoff data collected by the U S Geological Survey and SFWMD for five small agricultural watersheds in the Lower Kissimmee River and Taylor Creek Nubbin Slough Basins which are within the Northern Everglades watershed to evaluate the performance of current runoff estimation techniques based on NRCS s equation The watersheds ranged in size from 20 to 3600 acres and included improved and unimproved pasture Runoff data for these watersheds was plotted against rainfall and compared to the predicted runoff for seven models that all rely on the NRCS runoff equation They found that methods relying on measured water table elevations to assess the antecedent moisture condition
61. oks can be created on the desktop The model workbook is a large file with extensive computations embedded throughout Depending on the user s hardware and software it may be slow to run and older systems may not be able to load the model at all Calculations are controlled by the input system and may take some time to run Do not interrupt the calculation process unless you find the model unresponsive which will require the model to be shut down and restarted If this occurs your system may not have the ability to run the model When the PWRM Model workbook is first opened a message box may appear asking if you want to update data from an external source Select Don t Update and the data input menu system will start up Depending on your security settings you may be asked to enable macros The Client Data workbook will automatically be opened and then both workbooks will be disabled leaving the input menu enabled It is not intended that the user enter data directly into the workbook without sufficient training and understanding of the entire model functionality The workbook consists of nine different worksheets that are interconnected by the equations and processes embedded in the workbook If the user enters data or otherwise modifies anything directly into the workbook without using the data input menu system 1t may result in errors being generated that cannot be cleared without a full understanding of the embedded equations and proc
62. om right of the screen The form will be cleared for the next weir to be entered If you are editing a basin previously entered or need to change any data just entered select the weir you want to modify from the Weir Number Name drop down list Page 49 and then use the same processes previously described to Modify or Delete Click on the next tab to move to the next structure type Data Input Florida Ranchlands Environmental Services Program 3 Clear Current Project FRESP PROJECT DATA Wala f Project Service Area Acres E PrewMd C PostwMa aes L Prowect Basin Bazin Area Acres Run the Model C New f Existing County Watershed Area Acres F esulta Basin Number of Basins C New f Existing Copy Pre to Post Wiha Switch between Pre 4 Past SI Ditch Storage Impoundment Landuse Basin Stage Area Imp Stage Area Trend Analysis Horizontal Seepage Vertical Seepage Structures Number of weirs 0 ka Number of Weirs Recorded 0 Add Modify Delete Source Basin C Impoundment Weir Height t Feet Weir Number Mame T Top Width Feet Weir Type if Receiving Body Weir width Feet 4 weir Fixed Crest Elevation i Feet Web Season Elevation i Feet Dry Season Elevation i Feet Motch Angle Degrees Top Elevation i Feet Figure 13 Structures Weirs 15 Structures Pumps Figure 14 This is the fourteenth
63. one must expect an error introduction when uncorrelated rainfall and E data sets are used The error should be most pronounced during periods of persistent rainfall Validation runs indicated that the error is somewhat averaged out over a year s time but significant deviations can be seen between model computed and measured discharges when compared over shorter periods of time Daily values can deviate significantly As more correlated E and rainfall data becomes available the model user should employ the correlated data Certainly when the model is run in real time for site compliance monitoring correlated data from the closest weather station should be used in lieu of the average E values Vegetation Evapotranspiration Evaporation from a free water surface E is somewhat different than evapotranspiration from a vegetative cover ET Jones J W et al 6 discussed that the difference is largely due to differences in the reflectivity of the surfaces which in turn affects the net incoming solar radiation Ra This difference is found not only between water and vegetated surfaces but also between the various types of vegetated surface e g grass versus trees Accordingly free water surface evaporation rates E is converted to ET via the introduction of two coefficients The first coefficient converts Eo to a reference ET defined as ET for a short well watered grass surface as follows ET ET x K 13 Where
64. osed irrigation strategy The PWRM does not have the capability to automatically determine when and how much irrigation water could be applied Irrigation water pumped from outside surface sources can also be included in the model as an offsite inflow Horizontal Ground Water Seepage Horizontal seepage of groundwater in ranches within the North Everglades Basin is predominantly shallow and horizontal above an impermeable layer Horizontal seepage can be to or from the ground water to ditches or from above ground impoundments Regardless of the situation a simple and useful formula developed by Darcy can be used to estimate horizontal seepage rates The Darcy velocity is expressed in one dimensional flow above the hardpan as v Kx H H2 L 20 Where v Darcy velocity feet day K soil hydraulic conductivity feet day H H2 elevation of the ground water minus the ditch water elevation feet L distance water travels in the soil feet The seepage rate per unit width of flow area q is computed by q v x H H2 2 where q lateral seepage per unit width feet day 21 Horizontal seepage HSP to or from the vegetated area and a surface water source that 1s either adjacent to or within the site would then be computed by multiplying q by the length of the external adjacent ditch or by two times the length of the internal ditch In the case of an impoundment that is located next to a ditch the actual value of L should
65. osite direction The data requirements for these three types are gt Maximum Distance to Surface Water Conveyance or the distance the water would have to move from the source to the receiving body This might be the center of a pasture to the nearest ditch or to the impoundment or from a ditch Page 43 11 near the impoundment This distance is generally not going to be more than a couple of hundred feet since the driving head will be relatively small any further away than that gt Length of Interface would be the total length of ditch adjacent to the pasture or 1f it is internal to the pasture it would be twice the length accounting for seepage to the pasture from both sides Where pastures are criss crossed by ditches the length would include all of them and can get quite large The impoundment interface would be the length of the side s of the impoundment adjacent to the pasture or ditch gt Tailwater Elevation is not required for the first three interface types as the model calculates the elevations each day The Tailwater Elevation is required for the second three types see below gt Depth to Hardpan should be estimated from site specific data or soils information This represents the height of the flow path The 4 5 and 6 types of seepage interfaces represent water moving out of the basin or impoundment The data requirements are the same as the first three interface types but a Tailwater Elevation is req
66. ow to site manually input by the model user or by pump IR irrigation since most ranches seep irrigate irrigation is input to the surface storage and connected to the vegetated surfaces via the horizontal seepage component PU pumped outflow to an above ground impoundment or offsite ED emergency overflow from an impoundment Impoundments are categorized as depressional and above ground with pumped inflow Depending on the type of impoundment some of the terms are deleted The general water balance for accumulated surface storage in these features is as follows SSn SSy 1 Pne Ry Eon 1 CD y 1 HSP y VSP y PU n1 ED Na 3 Page 10 Where N day for which computation is done P precipitation R runoff from vegetated surfaces applies only to depressional impoundments E direct evaporation from open water surfaces CD surface discharge out of the impoundment control structure to offsite HSP and VSP horizontal and vertical seepage out of the impoundment depressional impoundments can have horizontal seepage into them PU pumped inflow from onsite connected storage or from offsite source to impoundment applies only to above ground impoundments ED emergency overflow from above ground impoundment when water level exceeds design maximum stage of above ground impoundment or rim elevation of depressional impoundment D Precipitation Ten years of SEWMD daily rainfall data measured at their Okeechobee Fiel
67. r hold these additions without spilling out onto the rest of the site If the elevation of the connected surface storage exceeds the rim elevation of the depressional impoundment the storage on top of the impoundment is accounted for in the stage storage data provided by the user If the amount of water added to the connected surface water storage results in a stage above the basin boundary elevation the model assumes the excess water sheet flows from the site and that amount is deducted from the connected storage volume The model re computes the water table onsite surface storage and impoundment elevations after making the additions and subtractions above These data are then used as initial conditions for the next day of the model run This process goes on for every day of the model run When finished with the above computations for each day the model totals on a monthly and annual basis the rainfall surface discharge change in volume of water stored onsite sheet flow out vertical seepage out and evaporation delineated into open water E and vegetation Page 21 ET Rainfall plus offsite inflows and irrigation minus surface discharges and sheet flow out the basin boundary equals retention O Logic Tests There are numerous logical functions embedded in the model computations to keep the PWRM from applying the formulas when they are not appropriate or creating deducting water that is not really there Some examples are 1 Ifthe pot
68. s such as the Penman or Blaney Criddle formulas The Penman equation is potentially more accurate as it takes into account many more climatic factors than the Blaney Criddle However the data needed to make the Penman computations are often unavailable for a specific site Accordingly Penman ET computations are usually made from data collected at nearby weather stations that do monitor the requisite meteorological parameters The historic monthly average ET rates computed in this manner 5 6 are then assumed to be representative of average daily ET rates within that month divided by the number of days within the month The open water surface ET rate is adjusted for vegetation through two methods Recent modifications to the Penman equation attempt to adjust several parameters to directly compute ET for a reference crop which is defined as a short well watered grass Another method to obtain the reference crop ET is just to apply a constant reduction Page 7 factor reference crop ET 70 of open water ET Both methods provide reasonable approximations ET rates for other types of vegetation are computed by the application of empirical coefficients that account for the type of crop and growth stage While these models do a reasonably good job predicting ET when water is readily available to the plant they overestimate evapotranspiration of rain fed vegetation experiencing less than optimum moisture conditions unless appropriate adjus
69. site surface water elevation If the user doesn t provide elevation data for the downstream end of the ditch or culvert the user must enter a water surface gradient to complete the calculation Pumps Surface water pumps can be included in the model to fill above ground impoundments and or discharge water from the site The user is required to input a nominal pump capacity an on elevation and if desired hours of operation per day The PWRM will operate the pump at its nominal daily rate in the discharge mode based on the model computed onsite surface water elevation the specified on elevation and the operating time However if there isn t enough water left in the onsite surface storage the pump will remove only the amount available If a particular site includes pumped offsite inflow the inflow is handled like a gravity inflow That is the user must provide a table of daily inflow volumes based on some pumping strategy N Computational Sequence l On day one of the model computation the model uses assumed initial conditions for on site groundwater and surface water stages elevations and the model partitions the total area into the inundated area connected surface storage and vegetated area Daily rainfall is applied to each of the three water balance components two if no impoundment is included If there are other sources of water like irrigation or inflow from another basin those amounts are added to the surface s
70. soil is numerically negative As discussed below in Section 4 F the difference P R is called total infiltration TT TI is further delineated into infiltration that remains in the vadose zone VI and infiltration that percolates down to the water table phreatic zone PI The PWRM tracks accumulated moisture content in the vadose zone to modify ET for drought conditions but does not track accumulated storage in the phreatic zone see Section 4 F However the PWRM does track the elevation of the phreatic zone surface water table as water 1s added and depleted to determine if the vegetation is in a drought condition For inundated surfaces that are hydraulically connected ditches to the site surface water discharge points the water balance for accumulated surface storage 1s as follows SSn SSy 1 Pn Ry Eon 1 D y 1 SF y 1 HSPN 1 VSP n1 OF n i IR yn 1 PU n1 ED N1 2 Where N day for which computation is done P precipitation R runoff from vegetated surfaces E direct evaporation from open water surfaces D surface discharge out of the site discharge points D can be negative if backflow occurs SF sheet flow discharge out of the site when the elevation of the stored water exceeds the elevation of the drainage divide HSP and VSP horizontal and vertical seepage either out of the site or to adjacent vegetated surfaces seepage into the stored water is numerically negative OF offsite infl
71. sture land and some wetlands Ditches are usually a small component of the area and storage across the basin They are typically narrow and deeper with steep side slopes Wetlands are typically bigger and shallower areas with very gradual side slopes and are typically found only at the lower elevations of the basin Pastures are usually the largest landuse component with more gradual slopes at the higher elevations A typical dataset for each relationship will often have three distinct sections in the curve that usually coincide fairly well with the three different landuses ditches wetlands and pastures To provide more accurate estimations of the relationships the model allows the user to break each equation into two or three parts by adding breakpoints into the calculation process The breakpoints identify the stage at which the equations should change from one to the next For example if the stages go from elevation 10 to 50 and breakpoints are added at 15 and 25 the model will use the first equation to calculate from 10 up to and including 15 the second equation to calculate from 15 up to and including 25 and the third equation to calculate from 25 up to and including 50 Page 40 Data Input Florida Ranchlands Environmental Services Program Clear Current Project FRESP PROJECT DATA wi y er l E E O PoE Froject Williamson Cattle Company Serice Area Acres 653 00 Save Project Basin 1 kd Bas
72. tab from the left of the row of tabs in the upper middle section of the main screen The Structures tab opens a sub menu set of four tabs representing each of the available structure types The fourth type is Pumps and allows four different pumps to be entered depending on the source and receiving body of the pump s If you have multiple pumps discharging from the same source to the same receiving body they will need to be grouped into a single pump Select the number of pumps you want to enter from the drop down list For the first pump click on the button representing where the pump discharges from source and then click on the button representing where the pump discharges to receiving body Page 50 Enter a Pump Number Name identifying it It 1s recommended the pumps be given meaningful names if possible to facilitate future data review Data Input Florida Ranchlands Environmental Services Program Clear Current Project FRESP PROJECT DATA WMA eae oo Project Service 4rea Acres Pewa PostiwhA AR See Project Basin Basin Area Acres Run the Model ens Existing County Jo Watershed Area Acres l Results Basin Humber of Basing C New f Existing Copy Pre to Post wih Switch between Pre Past Eee Ditch Storage Impoundment Landuse Basin Stage Area Imp Stage Area Trend Analysis Horizontal Seepage Vertical Seepage Structures Number of Pumps
73. th pre and post data already exist Clicking this button allows you to quickly switch back and forth between the Pre and Post data for the current project and basin without re selecting the information The Clear Current Project button at the top right corner of the screen will clear all of the menu screens and allow you to select another project and or basin or enter a new one without leaving the data input system Page 28 Data Input Florida Ranchlands Environmental Services Program Clear Current Project FRESP PROJECT DATA Wal hala f j Project Service Area Acres C Pre WkiA C Posttw Ma Prnject Basin i Basin Area Acres urthe Made C New C Existing County Watershed Area acres Beers Basin Humber of Basins f C New C Existing Copy Fre to Post WMA Switch between Pre Post ae i UPSTREAM BASIN Basin Area Acres ls there an Upstream contributory Yes basin Initial Depth to Water Table Inches Ives how many Maximum Basin Elevation Feet Select the upstream basin Ct Basin Overflow Elevation Feet add E elete ADDITIONAL DATA INPUT m DOWNSTREAM BASIN Does this basin discharge into a i es downstream basin Offsite Inflow Irrigation lf ves how many TailwaterData Evaporation Data Select the downstream basin Flowing Wells f Taihwater Recovery Add Delete Continue Check all
74. that apply Figure 1 Project Data and Basin Information The last set of boxes on the right will already be populated if you selected an existing project and an existing basin If you selected an existing project and are entering a new basin or you are entering a new project then all four boxes will need to be entered Following is a description of each of these fields gt Service Area This is the area within the basin being entered that the landowner agrees to place into service meaning that there may be times when the land is inundated for longer periods of time in the Post WMA condition than is currently happening in the Pre WMA or existing condition gt Basin Area This is a single contiguous piece of land that is hydrologically separated from surrounding land by natural or man made features gt Watershed Area When there are multiple basins this is the sum of the areas of all of the basins This may be larger than the project area if there are offsite contributing inflows gt Number of Basins The total number of basins within the watershed Page 29 Until all of the project data has either been entered or selected from existing data none of the other input menus will be enabled Once you have entered the necessary data click Save to enable the other input menus The four buttons on the right side of the screen are self explanatory Depending on certain conditions one or more of these buttons may be disabl
75. the Current data section and then select a Trendline Type from that dropdown box Click on the Update Plot button each time you change the breakpoint or the equation type The model will reset the graph from the minimum elevation up to the breakpoint elevation as the maximum You can then try out the different equation types to see if you get a better fit If you don t like the fit of any of the equations you can change the breakpoint elevation and then try the different equations again Once you get a good fit you can try different equations for the remaining dataset to see if you can find a good fit If you can t find a good fit you can enter a second breakpoint elevation and the model will allow you to go through the same process by selecting on the 3 1 Equation radio button or the tab above the graph It will often be necessary to move backward and forward trying out different breakpoints and equations Note that if you change the first breakpoint to an elevation equal to or higher than the second breakpoint the second breakpoint and the third equation will be cleared and you will need to re enter another one if necessary Once complete you will have one two or three equations the model will use to represent the Storage Stage relationship When you are satisfied with all of the equations you have selected click on the Save Equation button at the bottom center of the screen Caution clicking on the Save Equation
76. the AMC However research by Jaber F H et al 9 showed that a soil water table rises much higher than would be predicted by dividing the amount of applied water by the soil porosity They found that the observed rise was better predicted by using much smaller specific storage values It was surmised that this occurs due to air entrapment and partial filling of the soil pores during initial infiltration This further supports the use of AMC data to compute changes in the water table and S After the model has computed all of the inputs and outputs to the water table from the previous day the depth to the water table is recomputed for the following day as DWT DWT T PIn 1 io HSPN VSPnN 1 ETy 1 AMC 12 Where DWT depth to water table feet AMC available moisture capacity weight averaged over the surficial soil strata inches of water per foot of soil HSP and VSP horizontal and vertical seepage out of the phreatic zone PI amount of the total infiltration TI from the previous day rain that ends up in the phreatic zone ET Evapotranspiration that depletes water from the phreatic zone water table The new value of S is then computed by substituting the value of DWT into equation 11 Page 14 F Infiltration amp Soil Storage Once the surface runoff is computed for the daily rainfall total infiltration TI into the soil is the difference of rainfall minus runoff assumes that the initial abstraction event
77. the input menu system and review the Output data in that workbook Refer back to Section 6 D for more information Remember for the results to be accurate you must 1 Run the Model with the Pre WMA data and click the Results button 2 Immediately after Run the Model with the Post WMA data and click the Results button Page 52 10 11 References Soil Conservation Service U S Department of Agriculture 1969 National Engineering Handbook Section 4 Hydrology Jacobs J M S L Mergelsberg A F Lopera and D A Myers 2002 Evapotranspiration from a wet prairie wetland under drought conditions Paynes Prairie Preserve Florida USA Wetlands Vol 22 pp 374 385 Capece J C K L Campbell L B Baldwin K D Konyha 1987 Estimating runoff volumes from flat high water table watersheds American Society of Agricultural Engineers Transactions Soil and Water Vol 30 5 pp 1397 1402 United States Department of Agriculture Natural Resources Conservation Service 2003 Soil surveys Florida Clark G A A G Smajstrla and F S Zazueta 1993 Atmospheric parameters which affect evapotranspiration Florida Cooperative Extension Service Institute of Food and Agricultural Sciences University of Florida Jones J W L H Allen S F Shih J S Rogers L C Hammond A G Smajstrla and J D Martsolf 1984 Estimated and Measured Evapotranspiration for a Florida climate crops and soils Bulletin 840 Tech Insti
78. the model output to actual measurements made at the currently participating ranches Since the model s major objective is to compute the volume of rainfall runoff and retention on a daily basis no attempt has been made to equip it to calculate instantaneous runoff rates peak runoff rates for specific design storm events or hydraulic parameters such as headloss velocity etc This does not detract from the accuracy of the model in accomplishing its objectives and is well suited to the daily rainfall data available to accomplish the water balances While it is true that the duration and intensity of a rainfall event can affect the amount of storage and discharge sufficient instantaneous rainfall data are not available to compute a probabilistic distribution beyond the total daily volume of precipitation The PWRM calculates water balances without knowledge of where features are located on the site no spatial awareness Accordingly it is not necessary to identify specific locations of natural and WMA features Each feature is simply represented as a water balance component that is linked to other features through appropriate mechanisms For example lateral seepage from vegetated areas to surface water features is computed using model generated daily water elevations in each component user provided dimensions to estimate the width and depth of the groundwater flow interface and an assumed flow length for computation of seepage via the Darcy equat
79. they will have to be grouped together The required data for the Impoundment is self explanatory with the graphic on the right side of the screen to use as a reference The Maximum Water Elevation is the same as the Impoundment Overflow Elevation and represents the elevation of water at which point no further storage can occur Typically this is an emergency outfall intended to release water either back onto the basin or another project basin or offsite depending on the situation Typically there will also be a control structure s to keep the water level in the impoundment at a lower elevation to accommodate Page 34 additional rainfall events Once you ve entered the required data click on the Add button Data Input Florida Ranchlands Environmental Services Program Clear Current Project FRESP PROJECT DATA a Ma Project Service 4rea Acres Prewha C PostiwhA ect Ez EE O e ed Basin Basin Area Acres i eb rte i New i Existing County Watershed Area Acres Eleni Basin Number of Basing C New C Existing Copy Pre to Post Wiha Switch between Pre 7 Post Close Basin Sails Ditch Storage Impoundment Landuse Basin Stage Area Imp Stage Grea Trend Analysis Horizontal Seepage Yertical Seepage Stri Mas Impoundment Elevation Feet Area at Max impoundment Elevation Area at blas Impoundment Elevation Acres hi a impoundment E wea i
80. ting gt Basin If you selected a New project the New basin button will automatically be selected If you selected an Existing project you can select either a New or Existing basin The next group of boxes to the right will either require you to enter the information or select from a list of values accessed using the down arrow key at the right end of each box If you selected a new project you will enter the project name in the top box the basin name in the next box and then select the county in the next box from the list of values If the project overlaps county boundaries select the county that includes the majority of the project If you selected an existing project select the project name from the list of values Then if you selected a New basin enter the basin name If you selected an Existing basin select the basin from the list of values If you selected an existing project then the county name will already be there The Copy Pre to Post WMA button under the County box will not be enabled until you have saved the Pre WMA data Once it is enabled you can click this button and then modify the necessary data for the Post WMA model run and save it In most cases you will want to use this to save time since most of the data does not change between Pre and Post conditions The Switch between Pre Post button under the County box will not be enabled unless bo
81. tments are made The effective root zone is viewed herein for modeling purposes as the depth to which a plant can readily consume water either directly or indirectly through capillary rise from the saturated water table phreatic zone and evapotranspire water at the plant s maximum seasonal rate Whenever the top of the phreatic zone recedes below the effective root zone the plant is assumed to receive water only from the vadose zone As moisture within the vadose zone is depleted ET rates diminish to the point of permanent wilt The partitioning of ET response based on water table depth and effective root zone is well documented and described by Jacobs J M et al 2 4 Technical Basis A PWRM Water Balance Partitioning The PWRM is a one basin model It 1s assumed that the drainage divides 1 e site boundaries have been carefully identified by the user such that it can be assumed that there is no sheet flow of water into the modeled basin from adjacent basins If the user wishes to route gravity flow from another upstream basin they must do so by pre inserting a daily flow dataset from a previous model run of the upstream basin into the current model Caution must be exercised in how this is done When two basins are hydraulically linked the stage in the downstream basin can to varying degrees modify the inflow from the upstream basin The PWRM partitions a modeled site into three separate water balance components 1 the vegetated
82. torage based on the daily flow data provided by user The NRCS runoff equation computes runoff from and total infiltration into the vegetated surface component and the runoff is added to the connected surface storage volume and depressional impoundment if there is one When a depressional impoundment is included the user must tell the model what percent of the vegetated drains to the connected storage with the rest draining to the impoundment Page 20 10 11 IZ 13 14 Depending on the water table elevation versus the effective root zone of the plants within the vegetated component the model decides how to prorate the total infiltration between the vadose and phreatic zones At the same time depending on the water table effective root zone relationship the model computes ET for the vegetated surface If the water table is within the effective root zone all the infiltration goes to the phreatic zone the plants ET at the maximum rate for that time of year and the ET water is deducted from the phreatic zone If not the model checks the moisture content of the vadose zone reduces the ET for the less than well watered condition and deducts the ET water from the vadose zone It also attempts to refill the vadose zone up to the maximum available water capacity and if there is any infiltration left over it goes into the phreatic zone Open water evaporation is simultaneously deducted from the connected surface storage based on th
83. tute of Food and Agricultural Sciences University of Florida South Florida Water Management District 2008 Environmental Resource Permit Information Manual Vol IV Shaw J E and S M Trost Hydrogeology of the Kissimmee Planning Area South Florida Water Management District Technical Publication 84 1 Jaber F H S Shukla and S Srivastava 2006 Recharge upflux and water table response for shallow water table conditions in southwest Florida Hydrology Process 20 1895 1907 Woodward D E R Hawkins R Jiang A Hjelmfelt Jr J Van Mullem and Q D Quan 2001 Runoff Curve Number Method Examination of the Initial Abstraction Ratio USDA Natural Resources Conservation Service Water and Climate Center Abtew W 2005 Evapotranspiration in the Everglades Comparison of Bowen Ratio Measurements and Model Estimations ASAE Annual International Meeting in Tampa Florida Paper No 052188 Page 53
84. ually infiltrates As touched on earlier in the Manual the soil is delineated into two zones for modeling purposes the vadose unsaturated and phreatic saturated or water table Depending on the depth to water table top of the phreatic zone relative to the effective root zone of the vegetation the model partitions the TI into contributions to the vadose zone VI and the phreatic zone PI If the water table is within the effective root zone it is assumed that the vadose zone moisture content 1s equal to the available moisture capacity AMC there is no contribution to the VI and all of the TI is placed into the phreatic zone If the water table is below the effective root zone the model checks the moisture content within the vadose zone and contributes a portion of TI to the vadose zone up to the AMC Any TI not used to re supply the vadose zone is contributed to the phreatic zone via PI After the TI is appropriately distributed to the vadose and phreatic zones the change in the water table elevation is computed as shown in equation 12 G Water Surface Evaporation Evaporation from a free water surface Eo can be estimated by several existing models The Penman 1948 equation is probably the most widely accepted energy based method 5 This approach combines two components to estimate evaporation They are a radiative component and an advective component Although the Penman equation provides far better estimates of E than trad
85. uired Seepage calculations for these interfaces all start onsite using the model calculated elevation for the From component but you must provide an estimated Offsite Tailwater elevation for the To component based on field observations or other available information You can either enter a single offsite tailwater value in the box to be used for every daily calculation or you can include an Input data file in the Client Data workbook with different daily values for the 10 year period for each of these three interfaces you want to enter Use the Client Offsite TW4 Client Offsite TW5 and or Client Offsite TW06 worksheet s as appropriate If you choose to include an input data file leave the Tailwater Elevation box blank and the model will automatically use the input data file The user can enter each applicable interface only once by selecting an interface entering the data and clicking the Add button on the bottom left side of the screen If you are editing a basin previously entered or need to change any data just entered select the interface you want to modify from the Interface Type drop down list and then use the same processes previously described to Modify or Delete Click on the Continue button or the next tab to move to the next screen Vertical Seepage Figure 10 This is the tenth tab from the left of the row of tabs in the upper middle section of the main screen
86. utput workbook to a different named workbook to preserve the current results Alternatively additional worksheets could be added to the workbook to preserve the results but these worksheets must be given different names The user should be aware that adding too many worksheets in this workbook will quickly increase the size of the workbook and may slow down performance of the model in posting output to it Data Input Screens The screens are set up left to right in the order in which they should be completed when entering a new project In some cases data from a previous screen is necessary to complete calculations for another screen In these situations the model may show a delay in moving from one screen to the next as calculations are done and data updated When the user is working with an existing project the screens do not have to be accessed left to right so the user can jump around if they wish to make a modification without going through each screen to get to the one they want However movement may still show some delays as the same internal calculations and data updating will occur The top portion of the main screen is for overall project data and this section of the menu system remains visible to the user throughout the remainder of the screens The other screens are accessed by the tabs running from left to right across the upper middle of the main screen Each screen has a Continue button at the bottom that moves the user to
87. ven meaningful names if possible to facilitate future data review Select the Weir Type from the list of values and enter the Weir Width which is the length of the weir that allows water to discharge over it If the weir is not intended to be operated at different elevations seasonally enter a fixed elevation for the weir crest otherwise enter a Wet Season Elevation and a Dry Season Elevation The model will either use the fixed elevation if it is there or it will use December through May as the Dry season weir crest elevation and June through November as the Wet season weir crest elevation If the weir has a V Notch enter the angle of the notch in degrees Enter the Top Elevation of the weir or V Notch the Height of the weir and the width of the weir at the top of the structure The Receiving Body is selected from the list of values The choices are Offsite or Impoundment Note that even if the weir discharges to another basin in the project the model considers that to be Offsite for calculation purposes Click either the ON or OFF button to have the model use this structure in the model run or not This is most useful in testing different structural and operational WMAs without having to go back and forth re entering data Once you have entered the first weir click the Add button on the top right side of the screen The data will be saved and shown in the display box on the bott
88. y rainfall records over a 10 year period from a nearby weather station 1s adequate Vegetation Interception Evaporation Surface Runoff Direct P Rain __ _ I__ Impoundment Storage w 1777r A Ll SS L Horizontal Seepage Upstream Water Downstream Source Receiving Body Evapo transpiration Surface Runoff Horizontal Seepage Vertical Seepage Deep Groundwater Evapo transpiration Shallow Soil Storage Vertical Seepage Deep Groundwater Page 6 I Seepage I I impoundment I oo wane Horizontal Seepage Figure 1 Hydrologic Processes D Runoff amp Infiltration Of more importance is how the daily rainfall data is used to compute infiltration and runoff volumes For modeling purposes a site can be viewed as having two major components vegetated surface that 1s not under water and land surface that has standing water on it Rainfall is added directly to the inundated part Rainfall landing on the vegetated surface either directly evaporates from leaf surfaces infiltrates into the soil or runs off The rate at which rain will infiltrate the ground surface is generally quite high in this Basin Accordingly the runoff response is mostly determined by how much soil storage is available just prior to the rainfall event Capece et al 3 and much less so by ground slope and type of vegetativ

User Manual for the Potential Water Retention Model (PWRM)

Contents

Download Pdf Manuals

Related Search

Related Contents