Distribution of Runoff Sediments within Texas Southern High Plains Playa Wetlands.

Playa wetlands serve as natural catchments for surface runoff in the U.S. Southern High Plains (SHP) and are thought to serve as a major source of recharge for the Ogallala Aquifer. The functional importance of the approximately 20,000 playa wetlands is becoming more apparent with time and thought to be altered by sedimentation. Proposed sedimentation rates have been estimated to be as high as 4.8 mm/yr and 0.85 mm/yr for cultivated and native grassland surrounded wetlands, respectively. The purpose of this research was to evaluate cropland and grassland outerbasin management influences on playa wetland sediment distribution. Twenty-five soil samples were collected from each of six playa wetlands using a concentric circle sampling method. Playas in paired cultivated and grassland watersheds were sampled in Swisher, Floyd, and Briscoe Counties, TX. Samples were taken to Texas Tech University in Lubbock, TX and processed for soil-color and particle size distribution analysis. Watershed management influenced playa sedimentation. Soil color evaluation proved to be an adequate parameter to distinguish historically deposited sediments from the pre-settler sediments. The surface sediment soil color was predominately 10YR 3/2 (very-dark, grayish brown) for the Briscoe and Swisher County playas and 10YR 3/1 (very-dark gray) for the Floyd County playas. Measured sediment depth did not vary between land management. The cropland surrounded playas accumulated greater volumes of sediment than the playas surrounded by grassland.