Factors influencing runoff and sediment losses from the Belle Fourche River watershed in South Dakota.

摘要

In order to effectively manage, evaluate, as well as identify conditions that contribute to, and exacerbate sediment loads originating from rangelands, it is necessary that hydrology and associated biotic and soil factors be understood. Portable rainfall simulations were utilized on rangelands in the Belle Fourche River watershed, South Dakota, during the summers of 2007 and 2008 to quantify differences between runoff, time to runoff and sediment production from dense clay and clayey ecological sites. Vegetation and site characteristics were collected and used to model runoff, time to runoff and sediment production on both initial soil moisture and previously wetted plots.No differences between runoff rates or time to runoff between clayey and dense clay ecological sites were found despite having different vegetation characteristics. Sediment yields were approximately 50% higher from dense clay sites than for clayey sites. It was concluded that soil physical factors, mainly finer texture soils, may be responsible. Vegetation and site factors which influenced runoff varied between dense clay and clayey sites, but initial percent soil moisture was a primary driver on both ecological sites. Vegetation and site variables impacting sediment production were similar between sites and included vegetation height percent cover of canopy, litter, standing dead and slope.Effective models were developed for sediment production for both clayey and dense clay ecological sites. Value of models for runoff and time to runoff depended on ecological site as well as plot conditions. This study identified several vegetation factors that are critical in influencing sediment yield which can altered through grazing management to decrease sediment loading from rangelands and improve water quality in the Belle Fourche River.