Data from: Impact of antecedent soil moisture on runoff from a semiarid catchment

Antecedent soil moisture is an important factor in the generation of
runoff, but guidance for modeling moisture conditions in semiarid
catchments is limited and conflicting. In this study, the impact of
antecedent moisture was assessed at the plot scale (2.8 m2) using a
portable rainfall simulator, and at the catchment scale based on observed
precipitation and discharge for a 2.8 km2 watershed in central
New Mexico. Performance of three loss models commonly used for hydrologic
analysis in the southwestern U.S. was tested at both scales. High initial
moisture content led to substantially higher runoff ratios at both scales,
confirming the importance of antecedent soil moisture for runoff
predictions in semiarid drainages. Hydrologic parameters estimated based
on plot experiments, however, were highly variable and cannot easily be
upscaled to the catchment scale. Loss model performance was clearly scale
dependent: more simplistic (one- and two parameter) loss methods
out-performed a more complex (four parameter) model at the watershed
scale, while the opposite held true for test plot simulations. At the
catchment scale, all models performed poorly for small runoff events, but
yielded acceptable results for storms causing large discharges if
antecedent soil moisture was considered. Failing to account for antecedent
moisture led to simulated runoff volume errors up to one order of
magnitude.