Submitted to: Trade Journal Publication
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/1/2011
Publication Date: 5/3/2012
Citation: Villarreal, C., Zartman, R., Hudnall, W., Gitz, D.C., Rainwater, K., Smith, L. 2012. Spatial Distribution and Morphology of Sediments in Texas Southern High Plains Playa Wetlands. Texas Water Journal. 3(1):1-13. Interpretive Summary: Fresh water playa wetlands are shallow basin that catch water on the Southern High Plains. The water in playas is used by natural plant species, forage crops such as wheat, wildlife, and cattle. Playas thought to be the primary source of Ogallala Aquifer recharge. When the land around playas is tilled, sediments can wash into the playas, eventually filling them. We found that cropland playas had the most sediments being washed into them. But we also found that playas surrounded by grasslands and used primarily for ranching are also being filled, though much more slowly. This work is important because if the playas fill, more water could be lost to evaporation and less available for aquifer recharge.
Technical Abstract: Playas are depressional geomorphic features on the U.S. High Plains and about 20,000 Southern High Plains playa wetlands serve as runoff catchment basins, which are thought to be focal points of Ogallala aquifer recharge. Sediments in playas can alter biodiversity services, impede aquifer recharge, and increase evaporative water losses. The purpose of this study was to evaluate the effects of watershed cultivation systems on post-cultural sediment deposition in three pairs of cropland/native grassland playas in Briscoe, Floyd, and Swisher counties of Texas. A hydraulic probe was used to collect soil cores to 2 m or to refusal depth at 25 possible locations in each playa. Particle size distribution and soil color effectively identified sediment additions to the playas. Soil color transitions with depth from very dark grayish brown (10YR 3/2) to very dark gray (10YR 3/1) were always found in cropland playas, but not in grassland playas. Particle size distribution was more useful in identifying sediment distribution than type. Sediment volume in each playa was calculated from sediment thicknesses at the sampling locations and from sediment thicknesses interpolated between sampling locations using a kriging model. Sediment volume was directly related to watershed land use with more accumulated sediment in cropped playas than in grassland playas. Erosion of cultivated watersheds near playas contributes sediments that decrease playa depth and can result in increased evaporative water losses and decreased aquifer recharge.