Submitted to: Hydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2016
Publication Date: 8/26/2016
Citation: Gitz, D.C., Brauer, D.K. 2015. Trends in playa inundation and water storage in the Ogallala Aquifer on the Texas High Plains. Hydrology. 3(3):31. doi:10.3390/hydrology3030031.

Interpretive Summary: The Ogallala Aquifer is an important source of irrigation water on the Texas High Plains; however, significant decreases in saturated thickness threaten its future use for irrigation. A better understanding of the roles of playas, temporary surface ponds, in aquifer recharge is needed to establish sustainable levels of withdrawals. In this study, ARS scientists from the Soil and Water Management Research Unit (Bushland, TX) and the Wind Erosion and Water Conservation Research Unit (Lubbock TX) collected data regarding playa inundation, depth to groundwater, precipitation and land cover from 2001 to 2011 from four study areas on the Llano Estacado of the Texas High Plains. Twenty distinct inundation events were observed at the three playas between 2006 and 2010. For each of these inundations, water loss exceeded rates of evapotranspiration, implying that infiltration was occurring. Rates of infiltration based on playa water loss and volume of water in playas was more than sufficient to account for annual changes in groundwater. These results strengthen the argument that water storage in playas on the Llano Estacado is important source of water for aquifer recharge, and are of interest to water use planners and water policy makers.

Technical Abstract: The Ogallala Aquifer is an important source of irrigation water on the Texas High Plains; however, significant decreases in saturated thickness threaten its future use for irrigation. A better understanding of the roles of playas, ephemeral surface ponds, in aquifer recharge is needed to establish levels of withdrawals that meet established desired future conditions or sustainability. In this study, data regarding playa inundation, depth to groundwater, precipitation and land cover from 2001 to 2011 were collected and analyzed to ascertain associations between these characteristics for four study areas on the Llano Estacado of the Texas High Plains. Each area covered 40,000 to 70,000 ha. Three of the study areas in Hockley, Floyd and Swisher counties were chosen because their center contained a playa instrumented to measure weather and depth of inundation. Playa inundation in all four study areas was assessed by analyzing images from the National Agricultural Imaginary Program. There were 20 distinct inundation events at the three playas between 2006 and 2010. For each of these inundations, water loss exceeded rates of potential evapotranspiration by a factor of 1.6 to 15.7 times, implying that infiltration was occurring. Data on depth to groundwater were analyzed from 2000 to 2010 to determine annual changes of stored water. Annual changes in groundwater were strongly associated with annual rainfall but only weakly associated with surface area of inundated playas in late summer. However, rates of infiltration based on playa water loss versus potential evapotranspiration and volume of water in playas was more than sufficient to account for annual changes in groundwater. Land use adjoining the playas had less of influence on playa inundation than annual rainfall. These results strengthen the argument that water storage in playas on the Llano Estacado is important source of water for aquifer recharge.