Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: 12/14/2009
Publication Date: 12/18/2009
Citation: Rainwater, K., Ganesan, G., Gitz, D.C., Zartman, R., Hudnall, W., Smith, L. 2009. Estimating recharge through Playa Lakes to the Southern High Plains Aquifer[abstract]. American Geophysical Union. San Francisco, CA. December 14-18, 2009. Interpretive Summary:
Technical Abstract: In the Southern High Plains of Texas, it is accepted that focused recharge to the High Plains Aquifer (locally known as the Ogallala) occurs through over 20,000 playa lakes, which are local depressions that collect storm runoff. The amount and rate of recharge is not precisely known, and the impact of the land use surrounding each playa lake on the amount of runoff has not been quantified. Each playa exists within its own watershed, and many of those are cultivated, while others are surrounded by native grassland or conservation reserve program (CRP) lands. The amount of sediments entering most playas following cultivation has been substantial, but whether this erosion has had a harmful influence on recharge is unknown. Changing recharge rates can also impact the playa ecosystems that are pivotal to many types of local wildlife. Improved understanding of playa recharge is necessary for proper management strategies for long-term survivability of the Ogallala aquifer. Over the last four years, the research team selected and instrumented 30 playas (10 counties, one cropland playa, one native grassland playa, one CRP playa in each) for observation of their water budgets. To quantify recharge in each playa, data collection includes sufficient weather instrumentation to determine local precipitation and free water evaporation, as well as water level monitoring in the playa lake. The depth/area/volume relationship for each playa was developed by local GPS surveying. Between rainfall/runoff events, seepage through the playa bottom is calculated as the difference between the change in the volume of water stored in the playa and the calculated free water evaporation. The research team hopes to keep the instrumentation operational for as long as possible, hopefully several years, to observe enough inundation events to characterize a range of behaviors in the different playa basins. In this presentation, initial water budget analyses for several of the initially instrumented playa lakes are presented to demonstrate the variability in seepage rates between playas and for different inundation depths. After significant inundation time, seepage through the swelling Randall clay that forms the bottom of the playa lakes appears to decrease as the ponding depth drops, eventually going to zero in some cases.