Mini Disk Infiltrometer User`s Manual
Contents
1. a basic Microsoft Excel spreadsheet This spread sheet will calculate the slope of the curve of the cumulative infiltration vs the square root of time based on the data gathered in the above steps To use this spread sheet first make sure that your PC has Microsoft Excel installed Then do the following Minidisk Infiltrometer User s Manual 4 Collecting Data 1 Open the file You will see a table similar to the one above 2 Input the volume levels you recorded into the corre sponding volume column and correlated with the time column on the left You may need to extend the columns depending on how much data you have recorded The square root of time column and infiltra tion column will change automatically based on your data and the graph on the right of the table will update to reflect the changes 3 Save the data as a new spreadsheet on your hard drive Calculate Infiltration A number of methods are available for determining soil hydraulic conductivity from these data The method pro posed by Zhang 1997 is quite simple and works well for measurements of infiltration into dry soil The method requires measuring cumulative infiltration vs time and fit ting the results with the function FICC 1 where C4 m st and C m sg z are parameters C4 is related to hydraulic conductivity and C is related to soil sorptivity The hydraulic conductivity of the soil amp is then computed from L6 k F 2 wh2. water flow between soil particles becomes smaller and more tortuous and flow becomes more difficult Minidisk Infiltrometer User s Manual 3 Preparation 3 Preparation DV hblkAl9h To prepare the infiltrometer for measurement do the fol lowing 1 Fillthe bubble chamber by running water down the suction control tube or removing the upper stopper as shown Note Do not use distilled water Soil water has solutes and clays have salts on the exchange sites Using distilled water changes the ionic bal ance and may flocculate or disperse the clay in the soil upper stopper tube d y Z y V Z v P d di wo pH 4 A P IX 4 7 e 1 A suction control D gt Pig 2 Filling the upper chamber Minidisk Infiltrometer User s Manual 3 Preparation 2 Once the upper chamber is full slide the suction con trol tube all the way down invert the infiltrometer remove the bottom elastomer with the porous disk and fill the water reservoir Fig 3 Removing the bottom elastomer 3 Replace the bottom elastomer making sure the porous disk is firmly in place Minidisk Infiltrometer User s Manual 3 Preparation Choosing the Suction Rate Since different soil types will infiltrate water at different rates measuring the change of volume vs time can often be difficult particularly in a sandy soil where the water will infiltrate rapidly Therefore you can adjust the suc
3. Mini Disk Infiltrometer User s Manual Version 3 DECAGON DEVICES 2006 Decagon Devices Inc All rights reserved Decagon Devices Inc 950 NE Nelson Court P O Box 835 Pullman WA 99163 Minidisk Infiltrometer User s Manual Table of Contents Contents 1 Introduction 1 Welcome 14 rosvrk VERE VERE XS 1 Specifications alus ola ee Cree plos Contact Information lusus Warranty Information uuuuu The Infiltrometer 2 How it Works sse Seed A EACH 2 Features iile e a etes o bai eae dada 3 Hydraulic Conductivity 2005 4 Preparation 2 1 3 2692s 6 Choosing the Suction Rate 8 Placement saw sakes aa accen venies Dos 9 Collecting Data 10 Use the Spreadsheet Macro 1 Calculate Infiltration 2 000 12 References sese l4 Additional Reading ssueusuue 15 Maintenance 16 ClO GING eek ete EIE a er 16 Suction Tube 2d recess tegi ces 16 Minidisk Infiltrometer User s Manual Table of Contents Minidisk Infiltrometer User s Manual l Introduction 1 Introduction ST Welcome Welcome to the mini disk infiltrometer for measuring soil hydraulic conductivity The infiltrometer will enable you to measure the hydraulic conductivity of any soil accurately and affordably Specifications Total Le
4. e infiltrometer parts can be cleaned using mild soap and water The stainless steel disk can be cleaned with a brush or even run in a dishwasher Since it is stain less steel it will not rust cleans easily and won t snag or tear on rags when washing Suction Tube If the suction regulation tube is difficult to move use a small amount of vacuum grease to allow it to move more freely 16 Index I EE C collecting data 10 additional reading 15 calculate infiltration 12 references 14 using the spreadsheet macro 11 contact information 1 email 1 F fax number 1 H how the infiltrometer works 2 hydraulic conductivity 4 infiltrometer how to use 6 Introduction 1 M maintenance 16 cleaning 16 suction tube 16 17 P preparation 6 choosing the suction rate 8 placement 9 probe features 3 S seller s liability 2 specifications 1 T telephone number 1 W warranty 1 18
5. ere C is the slope of the curve of the cumulative infil tration vs the square root of time and A is a value relating the van Genuchten parameters for a given soil type to the 12 Minidisk Infiltrometer User s Manual 4 Collecting Data suction rate and radius of the infiltrometer disk A is com puted from _11 65 n exp 2 92 n 1 9 o7 A n 1 9 ar 3 11 917 S n 1 4 165 DexpTS 19 h g ar where z and Q are the van Genuchten parameters for the soil 7 is the disk radius and 7 is the suction at the disk surface The mini disk infiltrometer infiltrates water at a suction of 0 5 to 6 cm and has a radius of 2 2 cm The van Genuchten parameters for the 12 texture classes were obtained from Carsel and Parrish 1988 Values of A computed for the mini disk infiltrometer are given in Table 2 Table 2 van Genuchten parameters for 12 soil tex ture classes and A values for a 2 2 cm disk radius and suction values from 0 5 to 6 cm E ae a ee 0 5 10 20 30 40 5 0 6 0 Texture fn A 0 027 silty clay 0 005 62 6 3 6 5 67 6 9 7 1 7 3 0 008 13 Minidisk Infiltrometer User s Manual 4 Collecting Data 4 A quadratic equation is included in the Excel spread sheet Columns 2 and 4 from the table are used to pro duce an XY scatter plot to the right of the table This is used to calculate C4 which is the slope of this line denoted as y An example is
6. ers and growers in know ing how quickly water will infiltrate when applied to a given field or soil type Infiltration is also relevant in fields of study such as contaminant transport ground water recharge and ecosystem sustainability Because the infiltrometer has an adjustable suction 0 5 to 6 cm you can get additional information about the soil by eliminating macropores with an air entry value smaller than the suction of the infiltrometer This is done by con trolling the infiltration with a small negative pressure or suction When the water is under tension or suction it will not enter macropores such as cracks or wormholes but will only move into and through the soil as determined by the hydraulic forces in the soil Saturated conductivity is obtained when all the pores including the large ones such as cracks or wormholes are filled Macropore flow however is extremely variable from place to place and therefore difficult to quantify Infiltrating water under a tension prevents the filling of the macropores and gives a hydraulic conductivity charac teristic of the soil matrix and is less spatially variable Minidisk Infiltrometer User s Manual 2 The Infiltrometer Soil hydraulic conductivity is a function of water potential and water content of the soil The decrease in conductivity as the soil dries is due primarily to the movement of air into the soil to replace the water As the ait moves in the pathways for
7. low water to leak in open air The small diameter of the disk allows for undisturbed measurements on relatively level soil surfaces Once you place the infiltrometer on a soil water begins to leave the lower chamber and infiltrate into the soil at a rate determined by the hydraulic properties of the soil As the water level drops you record the volume at specific time intervals like every 30 seconds for a silt loam soil You can then plot this data using a spreadsheet included on CD ROM with the infiltrometer to calculate the hydraulic conductivity Minidisk Infiltrometer User s Manual 2 The Infiltrometer Features stopper p suction control tube bubble chamber chamber barrier Mariotte tube water reservoir Sintered steel disc Fig 1 Infiltrometer diagram Minidisk Infiltrometer User s Manual 2 The Infiltrometer Hydraulic Conductivity The mini disk infiltrometer measures the hydraulic con ductivity of the medium it is placed upon In Principles of Soil and Plant Water Relations by M B Kirkham 2005 hydraulic conductivity is defined as the meters per day of water seeping into the soil under the pull of gravity or under a unit hydraulic gradient This is different than infiltration rate which is defined as the meters per unit time of water entering into the soil regardless of the types ot values of forces or gradients Hydraulic conductivity is useful to scientists land manag
8. ngth 32 7 cm Diameter of tube 3 1 cm Sintered stainless steel disc 4 5cm dia 3 mm thick Length of suction regulation tube 10 2 cm Suction range 0 5 to 6cm of suction Length of water reservoir 21 2 cm Length of Mariotte tube 28cm Volume of water required to operate 135ml Contact Information To contact Decagon for customer support or questions E mail us at soils decagon com e Send us a fax at 509 332 5158 e Call us at 1 800 755 2751 US and Canada only or 509 332 2756 Warranty Information The infiltrometer has a 30 day satisfaction guarantee and a one year warranty Minidisk Infiltrometer User s Manual 2 The Infiltrometer 2 The Infiltrometer ae eee en The mini disk infiltrometer is ideal for field measure ments due to its compact size the water needed to oper ate it can easily be carried in a personal water bottle It is also practical for lab and classroom use in demonstrating basic concepts of soil hydraulic conductivity How it Works The upper and lower chambers of the infiltrometer are both filled with water The top chamber or bubble cham ber controls the suction The lower chamber contains a volume of water that infiltrates into the soil at a rate deter mined by the suction selected in the bubble chamber The lower chamber is labeled like a graduated cylinder with volume shown in mL The bottom of the infiltrometer has a porous sintered stainless steel disk which will not al
9. shown in the graph below 2 00 1 50 y 0 0028x 0 0575x R 0 9987 1 00 0 50 Cumulative Infiltration cm 0 00 Square Root of Time In this example the value of C is 0 0028 cm sl The soil is a silt loam so from Table 2 for 2 cm suction A 8 1 The hydraulic conductivity at 2 cm suction is therefore k 0 0028 cm s 8 1 3 45 x 10 cm s A much mote extensive discussion of tension infiltrome ter measurement and analysis is given in Dane and Topp 2002 p 888 896 References Carsel R E and R S Parrish 1988 Developing joint probability distributions of soil water retention characteristics Water Resour Res 24 755 769 14 Minidisk Infiltrometer User s Manual 4 Collecting Data Dane J H and G C Topp Eds 2002 Methods of Soil Analysis Part 4 Physical Methods Soil Science Soci ety of America Madison WI Kirkham M B 2005 Principles of Soil and Plant Water Rela tions Elsevier Academic Press Burlington MA pp 145 172 Zhang R 1997 Determination of soil sorptivity and hydraulic conductivity from the disk infiltrome ter Soil Sci Soc Am J 61 1024 1030 Additional Reading Clothier B E 2001 Infiltration Soi and Environmental Analysis Edited by Keith A Smith and Chris Mul lins 15 Minidisk Infiltrometer User s Manual 5 Maintenance 5 Maintenance feos eee MR cm Cleaning All of th
10. sible we also recommend using a ting stand and clamp to hold the infiltrometer in place Minidisk Infiltrometer User s Manual 4 Collecting Data 4 Collecting Data fn AO AUR MON EON To make the hydraulic conductivity measurement make sure you have first prepared the instrument as described in the previous chapter Then do the following 1 2 Record the starting water volume At time zero place the infiltrometer on the surface assuring that it makes solid contact with the soil sur face Record volume at regular time intervals as the water infiltrates The time interval you choose is based on both the suction rate you select and the soil type being measured For example a sand will typically be 2 5 seconds between readings a silt loam every 30 sec onds and a tight clay 30 to 60 minutes A typical data set will look like the first and third columns of Table 1 meg wea SECONDS el S Fig 5 Timed infiltration 10 Minidisk Infiltrometer User s Manual 4 Collecting Data Table 1 Sample infiltrometer data Time s sqrt t Mo Eo 0 0 00 95 0 00 30 5 48 89 0 39 60 7 75 86 0 58 90 9 49 83 077 120 10 95 80 0 97 150 12 25 77 116 180 13 42 75 129 210 14 49 73 142 240 15 49 71 155 270 16 43 69 1 68 300 17 32 67 18 Use the Spreadsheet Macro Your infiltrometer was shipped with a CDROM contain ing
11. tion rate to better accomodate measuring infiltration for the type of soil you are measuring For most soils a suction rate of 2cm should be adequate In particularly sandy soils where infiltration will occur very quickly an adjustment to 6cm may be helpful and for more compact soil where infiltration is much slower a suction tate of 0 5 is recom mended However we generally recommend that adjust ing the suction to rates other than 2cm should be reserved to more advanced users who are comfortable with the instrument and theory of operation To adjust the suction rate move the suction tube up or down so the water level is even with the desired suction tate matked on the side of the tube If the suction tube is difficult to move apply a small amount of vacuum grease on the tube to ease movement Small suctions allow large pores to fill large suctions allow only small pores to fill Minidisk Infiltrometer User s Manual 3 Preparation Adjustable suction tube Fig 4 Upper chamber and suction tube 4 If the infiltrometer is held vertically no water should leak out Placement The infiltrometer should be applied to a smooth spot on the soil surface If the surface is not smooth a thin layer of fine silica sand or diatomaceous earth can be applied to the area directly underneath the infiltrometer s stainless steel disk This will ensure good contact between the soil and the infiltrometer When pos
Download Pdf Manuals
Related Search