Sediment Accumulation in Semi-arid Wetlands of the Texas Southern High Plains

Abstract

The purpose of this study was to evaluate the effects of watershed management system on sediment deposition in playa wetlands, depressional geomorphic features that serve as watershed runoff catchment basins which are thought to be focal points for High Plains (Ogallala) aquifer recharge. Three pairs of cropland/grassland playa wetlands in Briscoe, Floyd, and Swisher counties of Texas were selected for the study. Watershed and annulus slopes, tillage index, shape indices, and watershed to wetland area ratio were used to evaluate the effect of watershed management on sediment deposition in playa wetlands. Sediment depth was directly related to watershed land use with more sediment accumulating in playa wetlands with cropped watershed than in grassland watersheds. Tillage index suggests that cropland watershed increased wetland sediment accumulation compared to grassland watersheds. The maximum slope in the annulus surrounding the wetland was positively correlated (0.959) to wetland sediment accumulation. Shape indices suggest that the more “circular” the watershed the less sediment accumulated. Slope of the annulus was significant while shape indices and the ratio of watershed to wetland areas were not significant in predicting wetland sediment accumulation.