BOREAS HYD-01 Soil Hydraulic Properties Summary The BOREAS HYD-01 team made several measurements related to soil moisture and soil properties. These soil hydraulic properties were determined at the flux tower sites based on analysis of in situ tension infiltrometer tests and laboratory determined water retention from soil cores collected during the 1994- 95 field campaigns. Results from this analysis are saturated hydraulic conductivity, and fitting parameters for the van Genuchten-Mualem soil hydraulic conductivity and water retention function at flux tower sites. The data are provided in tabular ASCII files. Table of Contents * 1 Data Set Overview * 2 Investigator(s) * 3 Theory of Measurements * 4 Equipment * 5 Data Acquisition Methods * 6 Observations * 7 Data Description * 8 Data Organization * 9 Data Manipulations * 10 Errors * 11 Notes * 12 Application of the Data Set * 13 Future Modifications and Plans * 14 Software * 15 Data Access * 16 Output Products and Availability * 17 References * 18 Glossary of Terms * 19 List of Acronyms * 20 Document Information 1. Data Set Overview 1.1 Data Set Identification BOREAS HYD-01 Soil Hydraulic Properties 1.2 Data Set Introduction Soil hydraulic properties were determined at the flux tower sites based on analysis of in situ tension infiltrometer tests and laboratory determined water retention from soil cores collected during the 1994-95 field campaigns. Results from this analysis are saturated hydraulic conductivity, and fitting parameters for the van Genuchten-Mualem soil hydraulic conductivity and water retention function at flux tower sites. 1.3 Objective/Purpose The objective of this study was to determine the soil hydraulic properties needed for physical simulation modeling of soil-vegetation-atmosphere-transfer processes. 1.4 Summary of Parameters The properties determined for each site were saturated hydraulic conductivity, KSAT; soil water retention using the van Genuchten (1980) function, THETA (H, N, ALPHA, SAT, RESID, M) where M = 1-(1/N); and unsaturated hydraulic conductivity using the Mualem (1976)-van Genuchten (1980) function, K (H, N, ALPHA, KSAT, M) where M = 1-(1/N). 1.5 Discussion In situ tension infiltrometer tests and laboratory soil core water retention data were combined to determine soil hydraulic properties at the sites of the flux towers operating during the 1994-95 BOReal Ecosystem-Atmosphere Study (BOREAS) field campaign. At each flux tower site, between 6 and 20 tension disk infiltrometer tests were performed at the soil surface (A-horizon). Laboratory soil core water retention data from the soil surface (A-horizon) were obtained from soil surveys conducted during 1993-94 by Darwin Anderson (southern sites) and Hugo Veldhuis (northern sites). Saturated hydraulic conductivity at each site was estimated by extrapolating the low tension conductivities of all tests to zero tension to obtain a site average saturated hydraulic conductivity. The unsaturated hydraulic conductivity function and soil water retention function were determined using the combined infiltrometer data of each site and the soil core water retention data. The tension infiltrometer data were determined at low tensions between 0 and 20 cm and the soil core water retention data were determined at high tensions between 100 cm and 15,000 cm, combining these two data sets using soil physics theory provides more information across the whole range of tensions from saturation at 0-cm tension to the permanent wilting point at 15,000-cm tension. The soil hydraulic properties were measured on a scale ranging from 5 to 20 cm, but distributed simulation models more often require these properties on a scale ranging from tens of meters to kilometers. Spatial variations in soil hydraulic properties of this data set were minimized by performing multiple tests at each site. The quality of this data set will be checked by using these parameters in a physics-based model (SWMS-2D finite element model of soil water movement) and comparing with soil moisture profiles collected at the sites during the BOREAS experiment. 1.6 Related Data Sets BOREAS TE-20 Soils Data over the NSA-MSA and Tower Sites in Raster Format BOREAS TE-20 Soils Data over the NSA-MSA and Tower Sites in Vector Format BOREAS TE-20 NSA Soil Lab Data BOREAS TE-01 Soils Data over the SSA Tower Sites in Raster Format BOREAS TE-01 SSA Soil Lab Data 2. Investigator(s) 2.1 Investigator(s) Name and Title Richard H. Cuenca, Professor Oregon State University 2.2 Title of Investigation Coupled Atmosphere-Forest Canopy-Soil Profile Monitoring and Simulation 2.3 Contact Information Contact 1 ------------ Shaun F. Kelly, Research Assistant Oregon State University Corvallis, OR (541) 737-6314 (541) 737-2082 (fax) kellys@pandora.bre.orst.edu Contact 2 ------------ Richard H. Cuenca, Professor Oregon State University Corvallis, OR (541) 737-6307 (541) 737-2082 (fax) cuencarh@pandora.bre.orst.edu Contact 3 ------------ David Knapp Raytheon STX Corporation NASA GSFC Greenbelt, MD (301) 286-1424 (301) 286-0239 David.Knapp@gsfc.nasa.gov 3. Theory of Measurements Disk tension infiltrometers are designed to measure soil water infiltration rates at a controlled negative water pressure or tension within a circular interface at the soil surface. The analysis of data in this data set is based on the approximation of flow from a circular source based on Wooding, 1968. From each test the steady state infiltration rate is used to calculate a conductivity, K, at the specified tension, H. The paired K, H data obtained from each test site runs across tensions ranging from 3 cm to 20 cm using two different disk radii. Saturated hydraulic conductivity and the unsaturated hydraulic conductivity at each site were summarized using the Mualem-van Genuchten model (Mualem, 1976; van Genuchten, 1980). Water retention function was simultaneously fitted to the data from the laboratory soil cores. 4. Equipment 4.1 Sensor/Instrument Description Disk tension infiltrometer: The disk tension infiltrometer is designed to measure unsaturated flow of water into soil. It consists of: 1) a bubble tower that controls tension at the soil surface, 2) a water reservoir from which water flows into the soil, and 3) a baseplate with a membrane to establish hydraulic continuity with the soil. The water level in the reservoir is monitored using pressure transducers and a datalogger to record infiltration rates during the tests. Infiltrometers with baseplate disk diameter of 8 and 20 cm were used. 4.1.1 Collection Environment The tension infiltrometer tests were performed throughout the 1994-95 BOREAS Intensive Field Campaigns (IFCs) from May to September. 4.1.2 Source/Platform The ground surface. 4.1.3 Source/Platform Mission Objectives The objective was to measure hydraulic properties of the soil. 4.1.4 Key Variables saturated conductivity hydraulic conductivity function water retention function 4.1.5 Principles of Operation The tension infiltrometer applies water to the soil surface at a constant tension and records the resulting infiltration rate in time. Hydraulic conductivities may be calculated using theoretical approximations of steady- state unconfined infiltration rates into the soil from circular sources. Hydraulic conductivities are determined at a number of tensions, and the hydraulic conductivity function is determined by fitting the appropriate function through the measured hydraulic conductivity versus tension data. 4.1.6 Sensor/Instrument Measurement Geometry The tension infiltrometer is set on the soil surface; therefore, only the hydraulic properties of the soil surface (A-horizon) are determined. 4.1.7 Manufacturer of Sensor/Instrument Tension infiltrometer Soil Measurement Systems 7266 N. Oracle Road Suite 170 Tucson, AZ 85704 (602) 742-4471 (602) 742-4379 or (602) 797-0356 (fax) The tension infiltrometer was automated by Shaun Kelly using pressure transducers and a recording datalogger. Pressure transducers Honeywell 136PC05G2, 5 PSI transducers available from Soil Measurement Systems Datalogger-Campbell Scientific CR10 Campbell Scientific, Inc. 815 W 1800 N Logan, UT 84321-1784 (801) 753-2342 (801) 750-9540 (fax) 4.2 Calibration Pressure transducers are calibrated in the lab using a standing water column. Transducer output in mV is linearly related to pressure. The infiltrometer is calibrated for the desired operating tensions before taking the unit to the field. Tension at the membrane on the baseplate in contact with the soil surface is controlled by the air entry ports in the bubble tower using one of three air entry tubes set at each desired tension. The air entry tubes are adjusted in the lab following the calibrating instructions in the manual. 4.2.1 Specifications 4.2.1.1 Tolerance None given. 4.2.2 Frequency of Calibration Pressure transducers have a tendency to drift and were calibrated before each IFC. Air entry tubes were calibrated once and required no further calibration unless it was desired to change the targeted tensions of 3, 5, and 15 cm tension. 4.2.3 Other Calibration Information Actual tensions applied were determined using the bottom transducer or the transducer mounted closest to the baseplate. The actual tension applied varied depending on the vertical distance between the baseplate and the bubble tower. 5. Data Acquisition Methods Operation of the tension infiltrometer is described in the user's manual supplied with each tension infiltrometer. The tension infiltrometer was modified to record the water level automatically with two pressure transducers and a datalogger. Each test was run at three target tensions 3 cm, 6 cm and 15 cm. Disk radii of 4 cm and 10 cm were used. Actual field operating tensions were calculated using the pressure recorded by the bottom transducer. 6. Observations 6.1 Data Notes None given. 6.2 Field Notes None given. 7. Data Description 7.1 Spatial Characteristics Multiple in situ measurements were made in the vicinity of the flux towers for each respective site. 7.1.1 Spatial Coverage The data represent determinations of the soil hydraulic properties based on measurements made in the vicinity of the flux tower. These measurements were made at the following tower locations: SITE LONGITUDE LATITUDE BOREAS_X BOREAS_Y ------------------------- ---------- ---------- ---------- ---------- SSA Young Aspen (YA) 105.32314W 53.65601N 374.607 310.761 SSA Old Black Spruce (OBS) 105.11779W 53.98717N 385.012 348.646 NSA Old Black Spruce (OBS) 98.48139W 55.88007N 778.216 613.516 NSA Old Jack Pine (OJP) 98.62396W 55.92842N 768.494 617.236 NSA Young Jack Pine (YJP) 98.28706W 55.89575N 789.845 617.424 SSA Old Aspen (OA) 106.19779W 53.62889N 317.198 303.403 SSA Old Jack Pine (OJP) 104.69203W 53.91634N 413.52 343.226 SSA Young Jack Pine (YJP) 104.64529W 53.87581N 416.988 339.008 7.1.2 Spatial Coverage Map None. 7.1.3 Spatial Resolution These data values were determined from a series of point measurements. 7.1.4 Projection Not applicable for point data. 7.1.5 Grid Description Not applicable. 7.2 Temporal Characteristics 7.2.1 Temporal Coverage In situ measurements were taken in conjunction with soil moisture monitoring during BOREAS IFC-1, -2, and -3 in 1994 and BOREAS IFC-1, -2, and -3 in 1995. 7.2.2 Temporal Coverage Map None. 7.2.3 Temporal Resolution Not applicable. These soil properties do not change significantly with time. 7.3 Data Characteristics Data characteristics are defined in the companion data definition file (h01_shd.def). 7.4 Sample Data Record Sample data format shown in the companion data definition file (h01_shd.def). 8. Data Organization 8.1 Data Granularity All of the Soil Hydraulic Properties data are contained in one dataset. 8.2 Data Format(s) The data file contains a series of numerical and character fields of varying length separated by commas. The character fields are enclosed within single apostrophe marks. There are no spaces between the fields. Sample data records are shown in the companion data definition file (h01_shd.def). 9. Data Manipulations 9.1 Formulae Wooding's equation (1958): Q=pi*r^2*K*(1+(4*lc)/(pi*r)) Q is water infiltration [vol/time]. K is hydraulic conductivity [length/time]. r is disk radius [length]. lc is the macroscopic capillary length [length]. Gardner's hydraulic conductivity function (1958): K(H)=KSAT*exp(ALPHAG*H) ALPHAG is a fitted parameter. H is the soil water tension. KSAT is the saturated conductivity. K is the hydraulic conductivity. van Genuchten soil water retention equation (1980): THETA(H)=RESID+(SAT-RESID)/(1+(ALPHA*H)^N)^(1-(1/N)) THETA is the volumetric water content [vol/vol]. RESID is the residual water content at some large negative tension [vol/vol]. SAT is the saturated water content [vol/vol]. ALPHA is an empirical fitting parameter or (1/lc)[1/length]. N is a fitting parameter. H is the soil water tension. Mualem(1976)-van Genuchten (1980) unsaturated hydraulic conductivity function: K(H)=KDAT*(1-(|ALPHA*H|^(N-1))*(1+(|ALPHA*H|^N))^((1/N)-1))^2 / (1+|ALPHA*H|^N)^((N-1)/2*N) KSAT is the saturated hydraulic conductivity [length/time] All other variables are the same as those in the water retention equation 9.1.1 Derivation Techniques and Algorithms An average value for KSAT was determined by extrapolating a fitted Gardener. (1958) exponential function to zero tension using the low tensions from each sequence of infiltration runs. The parameters for the water retention and hydraulic conductivity were then simultaneously fitted using a nonlinear fitting routine. The variables optimized were the sum of the squared difference between the natural log of the calculated and the measured steady state infiltration rates for the hydraulic conductivity and the weighted volumetric water contents for the water retention function. The fitting parameters N, ALPHA, SAT (saturated volumetric water content) and RESID (residual water content) are subject to the following constraints: 0 < N < 1, 1 < ALPHA <2, SAT < observed maximum soil moisture, and RESID > 0.01. 9.2 Data Processing Sequence 9.2.1 Processing Steps None given. 9.2.2 Processing Changes None. 9.3 Calculations 9.3.1 Special Corrections/Adjustments None given. 9.3.2 Calculated Variables saturated hydraulic conductivity hydraulic conductivity water infiltration volumetric water content 9.4 Graphs and Plots See Sections 10 and 11 for graphs and plots that are applicable to those sections. 10. Errors 10.1 Sources of Error Possible sources of error are poor contact of the infiltrometer disk with the soil surface, which reduces the actual effective disk radius (up to 1 cm), and pressure transducer drift in the offset, which may affect the actual tension applied to the soil (+/-2 cm). There is no additional information available to provide a quantitative error analysis of this data. 10.2 Quality Assessment Soil bulk density was not measured in the field and is an estimated value. It is not a parameter used in the retention or conductivity functions and is provided for reference only. It is the value given in the laboratory soil core data performed independently by other BOREAS researchers (see Section 1.6, Related Data Sets). Where bulk density was not provided in other data sets, a value was estimated from known values of soils with similar texture. Saturated and residual volumetric water content, SAT and RESID, were not directly measured in the field. These values were treated as fitting parameters when calculating retention and conductivity functions. Appropriate limits were placed on these parameters based on observed minimum and maximum water contents observed in the field measured with a neutron probe and Time Domain (TDR). These values may not be the same as would be found during soil core analysis because of entrapped air, existence of macropores, etc. Nevertheless, these values gave the best fit to the limited set of retention data collected. 10.2.1 Data Validation by Source Data were validated by comparing calculated parameters with soils of similar texture from the UNSODA data base (United States Department of Agriculture (USDA) Salinity Lab). Parameters are currently being used in physics-based soil water transport models (HYDRUS and WAVE) to simulate soil water movement and for comparing to site measurements of soil water content observed at the BOREAS sites from 1994-96. 10.2.2 Confidence Level/Accuracy Judgment The authors feel that the quality of the data is very good for use at the tower flux sites because of the numerous measurements made at the sites. 10.2.3 Measurement Error for Parameters None given. 10.2.4 Additional Quality Assessments Quality assessments of the goodness of fit are shown in the following graphs of the hydraulic conductivity function and the soil water retention function for the north Old Jack Pine (OJP) site and the south Old Aspen (OA) site. Actual field data are plotted with the calculated values using the parameters determined. 10.2.5 Data Verification by Data Center The data were loaded into a data base table and reviewed to ensure that no errors occurred in loading the data. 11. Notes 11.1 Limitations of the Data As one moves farther from the site the variability of soils due to natural geologic soil genesis processes will limit the spatial extent of the data. Although these are point measurements, it is expected that these parameters will be used for modeling of soil water processes at sites with similar soils similar to those at the tower site. The parameters were derived from tension infiltrometer data from the surface of the first mineral soil layer at each site (A-horizon). Therefore, these parameters would most accurately represent the soil water properties of the top 15 cm of soil. Although caution should be used when extrapolating the use of these parameters to greater soil depths, it is expected that these parameters will be used to model soil water properties at depths greater than 15 cm. 11.2 Known Problems with the Data None given. 11.3 Usage Guidance See Section 12. 11.4 Other Relevant Information None given. 12. Application of the Data Set This data set is particularly useful for use in models needing soil water hydraulic properties. The data are derived from in situ measurements and parameters developed from the theories of soil physics. This data set can be used to convert water contents to corresponding soil water tensions and vice versa. This data set can also be used to determine the hydraulic conductivity of the soil when soil water content or tension is known. The data set can be summarized in the following plots of the conductivity and retention functions at each site. 13. Future Modifications and Plans These data are currently being used for calibration of a finite element model of soil water movement for the BOREAS tower sites. These data iares being used for initial calibration of the model. Model verification is being made using the soil water transect data collected during the 1994 IFCs and the data currently being collected at NSA-Old Black Spruce (OBS), Old Jack Pine (OJP), Young Jack Pine (YJP) and SSA-OBS, and OA. In the future, it is planned to calculate sorptivity parameters for soils at each site. 14. Software 14.1 Software Description Microsoft Excel for Windows 95, Version 7.0 HYDRUS - finite element model of soil water movement WAVE - finite difference model of soil water movement Mathcad, Version. 6.0 14.2 Software Access Microsoft Excel and Mathcad are proprietary software packages. The availability of HYDRUS and WAVE software is not known. 15. Data Access 15.1 Contact Information Ms. Beth Nelson BOREAS Data Manager NASA GSFC Greenbelt, MD (301) 286-4005 (301) 286-0239 (fax) Elizabeth.Nelson@gsfc.nasa.gov 15.2 Data Center Identification See Section 15.1. 15.3 Procedures for Obtaining Data Users may place requests by telephone, electronic mail, or fax. 15.4 Data Center Status/Plans The HYD-01 soil hydraulic properties data are available from the Earth Observing System Data and Information System (EOSDIS), Oak Ridge National Laboratory (ORNL), Distributed Active Archive Center (DAAC). The BOREAS contact at ORNL is: ORNL DAAC User Services Oak Ridge National Laboratory (865) 241-3952 ornldaac@ornl.gov ornl@eos.nasa.gov 16. Output Products and Availability 16.1 Tape Products None. 16.2 Film Products None. 16.3 Other Products Tabular ASCII files. 17. References 17.1 Platform/Sensor/Instrument/Data Processing Documentation Tension Infiltrometer User's Manual. Soil Measurement Systems, 7266 N. Oracle Road, Suite 170, Tucson AZ, 85704. 17.2 Journal Articles and Study Reports Ankeny, M.D., T.C. Kaspar, and R. Horton. 1988. Design for an automated tension infiltrometer. Soil Sci. Soc. Am. J. 52:893-896. BOREAS Experiment Plan. April 1994. Boreal Ecosystem-Atmosphere Study. BOREAS Science Team. Version 2.0. BOREAS Experiment Plan. 1995. Boreal Ecosystem-Atmosphere Study. BOREAS Science Team. Version 3.1. BOREAS Experiment Plan. 1996. Boreal Ecosystem-Atmosphere Study. (Explan-96, v2.0) BOREAS Science Team. 3-18-96. Vol. I and II. Cuenca, R.H., D.E. Stangel, and S.F. Kelly. 1997. Soil water balance in a boreal forest. Journal of Geophysical Research (BOREAS Special Issue) 102(D24): 29355- 29366. Gardner, W.R. 1958. Some steady state solutions to the unsaturated flow equation with application to evaporation from a water table. Soil Sci. 85:228-232. Hussen, A. A. and A.W. Warrick. 1993. Alternative analysis of hydraulic data from disc tension infiltrometers. 29:4103-4108. Jarvis, N.J. and I. Messing. 1995. Near-saturated hydraulic conductivity in soils of contrasting texture measured by tension infiltrometers. Soil Sci. Soc. Am. J. 59:27-34. Mualem, Y. 1976. A new model for predicting the hydraulic conductivity of unsaturated porous media. Water Resour. Res. 12:513-522. Perroux, K. M. and I. White. 1988. Designs for disc permeameters. Soil Sci. Soc. Am. J. 52:1205-1215. Reynolds, W. D. and D. E. Elrick. 1991. Determination of hydraulic conductivity using a tension infiltrometer. Soil Sci. Soc. Am. J. 55:633-639. Sellers, P., and F. Hall. 1994. Boreal Ecosystem-Atmosphere Study: Experiment Plan. Version 1994-3.0, NASA BOREAS Report (EXPLAN 94). Sellers, P., CO2 F. Hall. 1996. Boreal Ecosystem-Atmosphere Study: Experiment Plan. Version 1996-2.0, NASA BOREAS Report (EXPLAN 96). Sellers, P., CO2 F. Hall. 1997. BOREAS Overview Paper. JGR Special Issue (in press). Sellers, P., F. Hall, CO2 K.F. Huemmrich. 1996. Boreal Ecosystem-Atmosphere Study: 1994 Operations. NASA BOREAS Report (OPS DOC 94). Sellers, P., F. Hall, CO2 K.F. Huemmrich. 1997. Boreal Ecosystem-Atmosphere Study: 1996 Operations. NASA BOREAS Report (OPS DOC 96). Sellers, P., F. Hall, H. Margolis, B. Kelly, D. Baldocchi, G. den Hartog, J. Cihlar, M.G. Ryan, B. Goodison, P. Crill, K.J. Ranson, D. Lettenmaier, and D.E. Wickland. 1995. The boreal ecosystem-atmosphere study (BOREAS): an overview and early results from the 1994 field year. Bulletin of the American Meteorological Society. 76(9):1549-1577. Van Genuchten, M.Th. 1980. A closed-form equation for predicting the hydraulic conductivity of unsaturated soils. Soil Sci. Soc. Am. J. 44:892-898. Warrick, A.W. 1992. Models for disc infiltrometers. Water Resour. Res. 28:1319- 1327. Wooding, R.A. 1968. Steady infiltration from a shallow circular pond. Water Resour. Res. 4:1259-1273. 17.3 Archive/DBMS Usage Documentation None. 18. Glossary of Terms ALPHA is an empirical fitting parameter or (1/lc)[1/length] ALPHAG is a fitted parameter in the Gardner equation or (1/lc)[1/length] H is the soil water tension [length] K is hydraulic conductivity [length/time] KSAT is the saturated conductivity [length/time] lc is the macroscopic capillary length [length] N is a fitting parameter Q is water infiltration [vol/time] r is disk radius [length] RESID is the residual water content at some large negative tension [vol/vol]. SAT is the saturated water content [vol/vol] THETA is the volumetric water content [vol/vol] 19. List of Acronyms BOREAS - BOReal Ecosystem-Atmosphere Study BORIS - BOREAS Information System DAAC - Distributed Active Archive Center EOS - Earth Observing System EOSDIS - EOS Data and Information System GSFC - Goddard Space Flight Center HYD - Hydrology IFC - Intensive Field Campaign NASA - National Aeronautics and Space Administration NSA - Northern Study Area OA - Old Aspen OBS - Old Black Spruce OJP - Old Jack Pine ORNL - Oak Ridge National Laboratory PANP - Prince Albert National Park SSA - Southern Study Area TE - Terrestrial Ecology TDR - Time Domain Reflectometry URL - Uniform Resource Locator USDA - United States Department of Agriculture YJP - Young Jack Pine 20. Document Information 20.1 Document Revision Date Written: 18-Sep-1996 Revised: 05-Jun-1998 20.2 Document Review Date(s) BORIS Review: 05-Jun-1998 Science Review: 20.3 Document ID 20.4 Citation This data was collected by Richard Cuenca, Shaun Kelly, and David Stangel as part of the HYD-1 investigation of the BOREAS Project. 20.5 Document Curator 20.6 Document URL Keywords Unsaturated hydraulic conductivity Soil water properties Matric potential Infiltration Sorptivity Diffusivity Porous media Disc permeameters Macroscopic length scale HYD01_SOIL_PROP.doc 06/11/98