Playa lakes in the southern high plains: runoff, infiltration, and recharge

Authors: WEINBERG, ANDREW - Texas Water Development Board; OLDEN, MARK - Texas Water Development Board; Gitz, Dennis; BYARS, CODY - Texas Tech University

Submitted to: Government Publication/Report
Publication Type: Government Publication
Publication Acceptance Date: 1/4/2021
Publication Date: 1/4/2021
Citation: Weinberg, A., Olden, M., Gitz, D.C., Byars, C.J. 2021. Playa lakes in the southern high plains: runoff, infiltration, and recharge. Texas Water Development Board Numbered Report #386. Available:http://www.twdb.texas.gov/publications/reports/numbered_reports/doc/report386.pdf

Interpretive Summary: In the Southern High Plains ephemeral lakes known as playas are thought to act as focal points of Ogallala Aquifer recharge. Schemes have been proposed to enhance aquifer recharge from playas, but the economic feasibility has not been examined for the Southern High Plains. Scientists from the Texas Water Development Board (TWDB), the USDA Agricultural Research Service, and Texas Tech University examined the feasibility of using surface water collected in playas as a source of managed recharge for the Ogallala Aquifer. The TWDB field work took place from 2011 to 2017. The ARS field work occurred from 2006 through 2015 and was funded in large part through the Ogallala Aquifer Program. It was found that the greatest economic return from managing recharge will be from large, frequently wet playas in areas where 1) the current infiltration rate is low, 2) where the aquifer water level is currently depleted, and 3) where there is demand for groundwater for high-value applications such as dairies and feedlots, specialty crops, or small-scale municipal or industrial water supplies. This work is important because it defines conditions within which management of aquifer recharge from playas is economically feasible and so can help guide public conservation policy.

Technical Abstract: Much less water is available from playas than suggested by previous studies. Between 1996 and 2014, playas captured a total annual average water volume of less than 200,000 acre-feet. The maximum volume collected in any single time (July 2015) was under 800,000 acre-feet, even though 2015 was the wettest year on record for many locations in the Southern High Plains. The 200,000-acre-foot average volume represents approximately 10 percent of previous ‘conservative’ estimates by the Bureau of Land Management. Measurable infiltration occurred at all studied playas. Average infiltration rates ranged from less than 0.04 to over 0.8 inches per day for the instrumented playas. The daily infiltration rates at any single playa varied as a function of flood depth, following the general principles of flow through porous media. Infiltration varies as a function of soil texture and soil type across the study area. Most infiltration occurs as flow through the porous matrix of the soil rather than through macropores and cracks. Macropore infiltration is important only for a short period when runoff enters a previously dry playa. Macrospores typically do not extend through the entire depth of the clay-rich layer on the playa bottoms, and macropore flow is almost entirely taken up by re-wetting of the dry near surface soils. As a result, macropores contribute little, if any to deeper percolation and recharge. Recharge systems could potentially capture much of the water currently lost to evaporation, though the cost of constructing and maintaining recharge systems is high relative to volume available. Projects using recharge from large, deep playas to supplement small public water supply systems may be economically viable. Upland recharge basins taking advantage of higher inter-basin percolation rates and free or low-cost night-time electricity may be more feasible than direct modification of playa basins themselves.