Thursday, October 25, 2012: 11:05 a.m.
Playas are the dominant wetland type on the U.S. Southern High Plains and capture runoff during periods of heavy rainfall. Measuring functions of playa wetlands is important to evaluate their ecological services, which include encouragement of species biodiversity during their hydroperiods and recharge of the underlying High Plains (Ogallala) aquifer. Five pairs of playa wetlands, one surrounded by natural grassland and the other by cultivated cropland, were chosen in Floyd, Briscoe, Swisher, Hockley, and Bailey counties on the Texas Southern High Plains. Instrumentation at each playa allowed calculation of changes in free water evaporation and water stored over time. A water budget model calculated daily infiltration flux through the playa bottoms as the difference between the change in stored playa water volume and the evaporation loss between precipitation events. All five cropland playas and only two grassland playas had significant hydroperiods during the four-year study, and data collection will continue in the future to hopefully increase the number of observed hydroperiods in all the playas. The observed infiltration flux rates for the cropland playas averaged approximately 10 mm/d (range 2 to 20 mm/d) while the rates for the grassland playas averaged about 2 mm/d (range 1-3 mm/d). The preliminary results may be influenced by the presence of eroded sediments from the surrounding cropland, but more events are needed to differentiate between the impacts of the playa floor soils and the variations in the precipitation events and playa watershed characteristics that contribute to the hydroperiods.
