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Report on Ksat for NCSS 2007 Committee 4May 23, 2007

In the National Soil Survey Handbook (NSSH; section 618.50), saturated hydraulic conductivity (Ksat) is defined as“the amount of water that would move vertically through a unit area of saturated soil in unit time under unit hydraulic gradient.” Since measurements are difficult to make and are available for relatively few soils, estimates of saturated hydraulic conductivity are based on soil properties. Exhibit 618-9 in the handbook provides a guide for estimating Ksat from soil texture and bulk density with a guide for use with overriding conditions (USDA-NRCS, 2007). This guide is based onthe work of Rawls and Brakensiek (1983). Also, water movement through lithic and paralithic materials can be estimated from a guide in Exhibit 618-10 of the handbook. In NASIS, entries are made for high, low, and representative values of Ksat for each horizon. There has been no validation of the handbook Ksat models and their accuracy is questionable. There is a need for a more accurate Ksat model that is applicable to all soil types (including organic soils) andthat can estimateKsat from readily available properties in Soil Survey. Also, there is a need to have the estimate of Ksat available as a “calculation” in NASIS. Ksat algorithms can be programmed in NASIS (only at the national level) and made available to soil scientist through a dropdown menu.

In 2005, the NCSS Committee 4 recommended that a new committee charge be identified, which was “to evaluate and recommend saturated hydraulic conductivity (Ks) methods and algorithms for use in soil surveys.” The committee indicated that NRCS has rudimentary methods to estimate Ksat (USDA-NRCS, 2007), and better models are needed. There were six aspects of Ksat the committee recommended that needed investigation (USDA-NRCS, 2005). One of those aspects was to evaluate “algorithms for estimating Ks for the NASIS data population where measurements are not available.” This is the aspect of Ksat that I am doing some work on.

I am evaluating different Ksat models from the literature for possible use in a Ksat calculation (in NASIS) and possibly replace the Ksat estimation procedure (models) that is currently in the NSSH. Table 1 lists the Ksat models under evaluation, which includes the Ksat model in the NSSH. The overall goal of the project is to evaluate established (from literature) Ksat models and develop a Ksat calculation in NASIS. Because certain models work better on some soils and not others, the Ksat calculation could be made up of several Ksat models. Ksat would be calculated for mineral as well as organic soils, andfor lithic and paralithic bedrocks. The models would have input parameters that would be obtained or derived from properties that are available within NASIS. Specific project objectives are to:

  1. Compare various Ksat models from the literature against each other and determine, in general, where they fail or don’t work, and look at consistency among the models across a wide range of soils. This will be accomplished byprogramming the Ksat models (Table 1) into a NASIS report that exports the results along with the stored Ksat value and soil survey data into spreadsheets for statistical analyses. The report will be run on selected soil survey areas.Hopefully this will eliminate some of the Ksat models.Progress—Fifteen Ksat models have been programmed into a NASIS report (Util – comparison of Ksat models; NSSC data site). The programming is being checked for errors, and then analyses can begin.
  2. Compare the models against field measuredKsat data. There is measured Ksat data from Iowa covering a range of soils textures from clay to sand with corresponding pedon descriptions and lab data. The Iowa Ksat data was measured with an amoozameter (multi-directional Ksat). Measured versus predictedKsat will be compared graphically and statistically. If other data sets become available, they will be used.Progress—Field Ksat data was collected in Iowa across a range of soil textures as part of an unrelated study (conducted in October/November, 2006). All corresponding lab data is expected to be completed by the end of June, 2007. An Excel database is currently being constructed for comparison of measured versus predicted Ksat values.
  3. Compare models to vertical Ksat data (cores) taken from literature studies. A literature Ksat dataset was constructed in the 1990’s (Rawls et al., 1998) by NRCS. The database will be resurrected, verified, and newKsat dataadded.Measured versus predictedKsat will be compared graphically and statistically. Progress—A database of measured Ksat from the literature is being developed. The original dataset that was constructed in the 1990’s (Rawls et al., 1998) is the staring point for constructing this measured Ksat database.

Ksat models for organic soils are lacking in the literature. If anybody knows of any models, please let me know, or any other additional Ksat models. My contact information is at the end of this document. Any comments or suggestions are welcome.
Table 1. Saturated hydraulic conductivity models and associated input parameters.

Ksat Model/soil type / Input parameters†
Nemes et al. (2005) / Sand, clay, Db, OM
Rawls and Brakensiek (1985) / Sand, clay, porosity
Jabro (1992) / Sand, silt, Db
Saxton et al. (1986) / Sand, clay, saturated water content
Campbell and Shiozawa (1994) / Sand, clay
Puckett et al. (1985) / clay
Dane and Puckett (1994) / clay
Schaap (1999, Rosetta) / Sand, silt, clay, Db
Schaap (1999, Rosetta) / Sand, silt, clay, Db, 1/3 bar water, 15 bar water
Barr (2001) / Db, gravitational constant, fluid viscosity, hydraulic radius of pores, density of fluid, porosity
Baumer et al. (1994) / Very coarse, coarse, and medium sand; clay, silt, OM, CEC, Db, satiated water content, Dbovendry
NSSH (Rawls et al., 1983) / Db, texture class
Vereecken et al. (1990) / Sand, clay, Db, OM
Wösten et al. (1999) / Clay, Silt, topsoil (1,0), Db, OM,
Wösten et al. (2001)/sandy soils / Silt, Db, OM
Wösten et al. (2001)/loam & clay soils / Clay, Db, OM
Chapuis (2004)/uniform sand & gravel soils / Effective diameter, void ratio
Boelter (1969)/peat soils / Db

† Db = Bulk density; OM = Organic matter; CEC = Cation exchange capacity

References

Barr, D.W. 2001. Coefficient of permeability determined by measurable parameters. Ground Water 39:356-361.

Baumer, O, P. Kenyon, and J. Bettis. 1994. MUUF v2.14 User’s Manual. p. 42

Boelter, D.H. 1969. Physical properties of peats as related to degree of decomposition. Soil Sci. Soc. Amer. Proc. 33:606-609

Brakensiek, D.L., W.J. Rawls, and G.R. Stephenson. 1986. Determining the saturated hydraulic conductivity of a soil containing rock fragments. Soil Sci. Soc. Am. J. 50:834-835

Campbell, G.S., and S. Shiozawa. 1994. Prediction of hydraulic properties of soils using paricle-size distribution and bulk density data. p. 317-328. In: M .Th. van Genuchten et al. (eds) Proceedings of the International workshop on indirect methods for estimating the hydraulic properties of unsaturated soils. Univ. of California, Riverside, CA.

Chapuis, R.P. 2004. Predicting the saturated hydraulic conductivity of sand and gravel using effective diameter and void ratio. Can. Geotech. J. 41:787-795.

Dane, J.H., and W. Puckett. 1994. Field soil hydraulic properties based on physical and mineralogical information. p. 389-403. In: M .Th. van Genuchten et al. (eds) Proceedings of the International workshop on indirect methods for estimating the hydraulic properties of unsaturated soils. Univ. of California, Riverside, CA.

Jabro, J.D. 1992. Estimation of saturated hydraulic conductivity of soils from particle size distribution and bulk density data. Trans. ASAE 35:557-560.

Nemes A., W.J. Rawls, and Y.A. Pachepsky. 2005. Influence of organic matter on the estimation of saturated hydraulic conductivity. Soil Sci. Soc. Am. J. 69:1330-1337.

Pucket, W.E., J.H. Dane, and B.F. Hajek. 1985. Physical and mineralogical data to determine soil hydraulic properties. Soil Sci. Soc. Am. J. 49:831-836.

Rawls, W.J., and D.L. Brakensiek. 1983. A procedure to predict green and ampt infiltration parameters. p. 102-112. In: Advances in infiltration: Proceedings of the National Conference on Advances in Infiltration. December 12-13, 1983, HyattRegencyIllinoisCenter, Chicago, IL. ASAE Publ. 11-83.

Rawls, W.J., and D.L. Brakensiek. 1985. Prediction of soil water properties for hydrologic modeling. p. 3-299. In: E.B. Jones and T.J. Ward (eds.) Water management in the Eighties. Proc. of Symp. Sponsored by committee on Watershed Management, Irrig. And Drain. Div., Am. Soc. of Civil Engineers, New York.

Rawls, W.J., and D. Gimenez, and R. Grossman. 1998. Use of soil texture, bulk density, and slope of the water retention curve to predict saturated hydraulic conductivity. Trans. ASAE 41:983-988.

Saxton, K.E., W.J. Rawls, J.S. Romberger, and R.I. Pependick. 1986. Estimating generalized soil water characteristics from soil texture. Soil Sci. Soc. Am. J. 55:1231-1238.

Schaap, M.G. 1999. Rosetta Version 1.0. US Salinity Laboratory, USDA, ARS, Riverside, CA. Available online at

USDA-NRCS. 2007. National Soil Survey Handbook, title 430-VI. [Online] Available at .

USDA-NRCS. 2005. NCSS 2005 Committee 4: Water movement and water table monitoring in soil survey. p. 111-135. In: Proceedings of the 2005 National Cooperative Soil Survey Conference: Planning the new soil survey—personnel development, technology, standards and electronic delivery [Online]. May 21-26, 2005. Corpus Christi, TX. Available at

Vereecken, H., J. Maes, and J. Feyen. 1990. Estimating unsaturated hydraulic conductivity from easily measured soil properties. Soil Sci. 149:1-12.

Wösten, J.H.M., A. Lilly, A. Nemes, and C. Le Bas. 1999. Development and use of a database of hydraulic properties. Of European soils. Geoderma 90:169-185.

Wösten, J.H.M., G.J. Veerman, W.J.M. de Groot, and J. Stolte. 2001. Waterretentie-en doorlatendheidskarakteristieken van boven-en ondergronden in Nederland: De Straringreeks. (Water retention and hydraulic conductivity characteristics of top- and subsoils of the Netherlands: The Staring series). (In Dutch) ALTERRA Report Nr. 153. ALTERRA. Wageningen, The Netherlands.

Cathy Seybold

USDA-NRCS

NationalSoilSurveyCenter

Lincoln, NE

(402) 437-4132