Estimating Infiltration in the Upper Split Wash Watershed, Yucca Mountain, Nevada

The KINEROS2 rainfall-runoff model was used in this case Study to estimate plane and channel infiltration within the Upper Split Wash watershed on Yucca Mountain, Nev. Averaged over the watershed area, estimated mean annual runoff, channel infiltration, and bedrock infiltration were 3.6, 0.6. and 8.7 nm/year. Most overland flow resulted from saturation of thin soils during low-intensity winter storms. The greatest excess infiltration (the difference between actual infiltration and precipitation) occurs oil lower portions of hillslopes having deep soils receiving runoff from upslope areas. The greatest bedrock infiltration Occurs on hillslope areas with thin soils and high values of bedrock hydraulic conductivity (K-S). A sensitivity analysis Suggests that estimated runoff and infiltration rates are most sensitive to soil depth and are less sensitive to bedrock K-S, the soil hydraulic parameter defining field capacity and wilting point, the soil capillary drive parameter, and the antecedent precipitation index.