Applicability of targeting vegetative filter strips to abate fecal bacteria and sediment yield using SWAT

Abstract

Quantifying and evaluating effects of best management practices (BMPs) on water quality is necessary to maximize the effectiveness of BMPs for minimizing pollutants. Watershed-scale evaluation of effects of BMP implementation on fecal bacteria and sediment yield can be estimated using a watershed water quality model, and strategies for identifying critical areas in a watershed can be pollutant specific. The soil and water assessment tool (SWAT) model was used in the Upper Wakarusa watershed (950 km 2) in northeast Kansas to explore effectiveness of vegetative filter strip (VFS) lengths applied at the edge of fields to reduce non-point source pollution. The Upper Wakarusa watershed is a high priority total maximum daily load (TMDL) designation watershed for fecal bacteria in Kansas. This study characterizes fecal bacteria sources (human, livestock, and wildlife) and targets VFS to abate sediment and fecal bacteria pollution from the Upper Wakarusa watershed. Objectives of this study were to test the effectiveness of VFS lengths (0, 10, 15 and 20 m) for removing overland process sediment and fecal bacteria concentration, rank sub-watersheds after determining sediment and fecal bacteria contribution of each sub-watershed, and demonstrate the SWAT model's ability to evaluate effectiveness of VFS application to abate sediment and fecal bacteria using targeted and random approaches to select 10, 25 and 50% of the sub-watersheds. The 15-m VFS reasonably reduced fecal bacteria concentration in the watershed. The greatest difference between the target and random approaches to fecal bacteria reduction was at 50% VFS adoption; the target approach removed about 60% of fecal bacteria, and the random approach removed about 42%. For sediment yield, the greatest reduction was at 25% VFS adoption; the target approach removed about 63% of sediment yield, and the random approach removed about 33%. A targeted watershed modeling approach using SWAT was effective at reducing both fecal bacteria concentration and sediment yield.