HYDROLOGIC RESPONSES OF AN AGRICULTURAL WATERSHED TO VARIOUS HYDROLOGIC AND MANAGEMENT CONDITIONS1

Abstract

ABSTRACT: The hydrologic responses from an agricultural watershed in southeast Nebraska were investigated under an array of physiographic, hydrologic, meteorologic, and management conditions. For analytical purposes, the hydrologic responses were narrowed to include only runoff and sediment yield. The study was performed by utilizing the ANSWERS (Areal Nonpoint Source Watershed Environment Response Simulation) hydrologic‐simulation model. Results of this study indicate that, generally, nonstructural (agronomic) Best Management Practices (BMPs) have a more significant impact in controlling erosion and nonpoint‐source pollution than structurally oriented BMPs. The percentage of reduction in average soil loss as a result of changing tilage systems from conventional to chisel plow was in the mid‐40s. The corresponding percentages of reduction in sediment yield from the watershed under minimum tillage and no‐till systems were in the mid‐60s and mid‐80s, respectively. The impact of these management strategies on runoff varied considerably. That is primarily based on the watershed's antecedent soil moisture condition, land use, and the growth stage of crops. Generally, an intense, short, thunderstorm type of rainfall event had more relative impact on runoff, and therefore sediment yield than a long, gentle, and steady event.