Comparison of models for indirect estimation of water retention and available water in surface soils

Marcel Schaap, Attila Nemes, Martinus Th van Genuchten

Research output: Contribution to journalArticle

40 Citations (Scopus)

Abstract

Quantitative knowledge of the unsaturated soil hydraulic properties is required in most studies involving water flow and solute transport in the vadose zone. Unfortunately, direct measurement of such properties is often difficult, expensive and time-consuming. Pedotransfer functions(PTFs) offer a meansto estimate soilhydraulic properties based on predictors like texture, bulk density, and other soil variables. In this study, we focus on PTFs for water retention and show that systematic errors in five existing PTFs can be reduced by using water content-based objective functions, instead of parameter value-based objective functions. The alternative analysis was accomplished by establishing offset and slope coefficients for each estimated hydraulic parameter. Subsequently we evaluated these and six other PTFs for estimating water retention parameters using the NRCS soils database. A total of 47 435 records containing 113 970 observed water contents were used to test the PTFs for mean errors and root mean square errors. No overall superior model was found. Models with many calibration parameters or more input variables were not necessarily better than more simple models. All models underestimated water contents, with values ranging from -0.0086 to -0.0279 cm 3 cm -3. Average root mean square errors ranged from 0.0687 cm 3 cm -3 for a PTF that provided textural class average parameters to -0.0315 cm 3 cm -3 for a model that also used two water retention points as predictors. Available soil water content for vegetation was estimated with errors ranging from 0.058 to 0.080 cm 3 cm -3, depending on the model and the definition of available water.

Original languageEnglish (US)
Pages (from-to)1455-1463
Number of pages9
JournalVadose Zone Journal
Volume3
Issue number4
StatePublished - Nov 2004
Externally publishedYes

Fingerprint

pedotransfer function
pedotransfer functions
water retention
soil surface
water content
soil
water
soil transport processes
soil hydraulic properties
vadose zone
hydraulic property
solute transport
water flow
bulk density
comparison
soil water content
fluid mechanics
calibration
texture
soil water

ASJC Scopus subject areas

  • Soil Science

Cite this

Comparison of models for indirect estimation of water retention and available water in surface soils. / Schaap, Marcel; Nemes, Attila; van Genuchten, Martinus Th.

In: Vadose Zone Journal, Vol. 3, No. 4, 11.2004, p. 1455-1463.

Research output: Contribution to journalArticle

Schaap, Marcel ; Nemes, Attila ; van Genuchten, Martinus Th. / Comparison of models for indirect estimation of water retention and available water in surface soils. In: Vadose Zone Journal. 2004 ; Vol. 3, No. 4. pp. 1455-1463.
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