Estimation of Green-Ampt effective hydraulic conductivity for rangelands

Mary R. Kidwell, Mark A. Weltz, D. Phillip Guertin

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


Effective hydraulic conductivity (K(e)) is an important parameter for the prediction of infiltration and runoff volume from storms. The Water Erosion Prediction Project (WEPP) model, which uses a modified Green-Ampt equation, is sensitive to the hydraulic conductivity parameter in the prediction of runoff volume and peak discharge. Two sets of algorithms developed from cropland data to predict K(e) have previsouly been used in the WEPP model. When tested with data collected on rangelands, these equations resulted in low predictions of K(e) which significantly over-estimated runoff volume. The errors in runoff prediction were propagated through the model and resulted in poor predictions of peak discharge and sediment yield. The objective of this research was to develop a new predictive equation to calculate K(e) specifically for use on rangelands using field data collected in 8 western states on 15 different soil/vegetation complexes. A distinction was made between ground cover parameters located outside and underneath plant canopy in on effort to account for the significant spatial variability that occurs on most rangelands. Optimized K(e) values were determined using the WEPP model and observed runoff data. A regression model (r2=0.60) was then developed to predict K(e) using measured soil, canopy cover, and spatially distributed ground cover data from 44 plots. Independent rangeland data sets are now required to test the new equation to determine how well the relationships developed from the data used in this study extend to other rangeland areas.

Original languageEnglish (US)
Pages (from-to)290-299
Number of pages10
JournalJournal of Range Management
Issue number3
StatePublished - May 1997


  • WEPP
  • ground cover
  • hydrologic modeling
  • infiltration
  • runoff
  • spatial variability

ASJC Scopus subject areas

  • Ecology
  • Animal Science and Zoology


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