Estimating Effective Hydraulic  Conductivity ( Ke ) for the Rangeland  Hydrology and Erosion Model (RHEM)

Highlights Effective hydraulic conductivity ( K e ) predictive equations in all RHEM versions have satisfactory performance. New K e predictive equations were developed for RHEM applications over broader rangeland conditions. K e values on most rangelands can be estimated through readily measurable ground cover and soil texture data. Abstract. Effective hydraulic conductivity (K e ) is an important parameter for the prediction of infiltration and runoff by the Rangeland Hydrology and Erosion Model (RHEM). Three sets of equations to predict K e have previously been used in RHEM. These equations are mainly based on rainfall simulation data representing undisturbed sites and have not undergone comprehensive evaluation for various rangeland conditions, particularly after disturbances. The goal of this research was to evaluate these equations using independent data obtained from rainfall simulations conducted at multiple rangeland sites. Additionally, we developed and evaluated a new set of K e predictive equations applying readily measurable cover and soils data spanning a wide range of vegetation, soil textures, and disturbance conditions. The results show that all previous K e equations in RHEM have a “satisfactory” performance with index of agreement (d) > 0.75 and R 2 > 0.4. The new K e approach resulted in “very good” performance with d > 0.9 and R 2 > 0.5. The new set of equations enhances RHEM for applications over broader rangeland conditions, including sparse vegetation cover following disturbances or community transitions. Keywords: Disturbed Rangelands, Hillslope Runoff, Infiltration.