Playa Lakes in the Southern High Plains: Runoff, Infiltration, and Recharge

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Project Goals

• Overall Goal: Examine the feasibility of using surface water collected in ephemeral lakes (playas) on the Texas High Plains
• Phase 1: Quantify volume of water in playas and measure current recharge rates from selected playas
• Phase 2: Playa modifications to assess potential for increasing recharge to the Ogallala Aquifer (no funding for Phase 2)

Major Findings

The playa lake study focused on three main objectives:

• Objective 1: Determining how much water is captured in playas
• Findings: The 1996 to 2017 average annual volume of water captured in Texas playas is 221,000 acre-feet, or about 10 percent of a 1984 estimate by the U.S. Bureau of Reclamation.
• Objective 2: Estimating current infiltration rates at individual playas
• Findings: Average infiltration rates range from less than 0.04 to over 0.8 inches per day. Infiltration rates vary as a function of water depth, following the general principles of flow through porous media. Infiltration rates are highest in the southern and western parts of the study area where the predominant soil types are sandier.
• Objective 3: Clarifying recharge mechanisms
• Findings: We found that most recharge occurs via gradual percolation through the soil matrix following repeated flood events. Rapid infiltration through large cracks or burrows affected only the upper six feet of the soil profile and did not produce pulses of recharge to the aquifer.

Status

• Five years of Phase 1 monitoring has been completed. More than 100 flood events were observed, ranging in size from less than 1 acre-foot to nearly 1,000 acre-feet in volume.
• Access agreements were completed with 36 landowners.
• Monitoring equipment was installed in 38 playas in 13 counties across the Panhandle.
• Topographic surveys and satellite data were used to develop flood histories for 72 playas.
• Research cooperation was established with groups from Texas Tech, the US Department of Agriculture - Agricultural Research Service, and Clemson University.
• Intensive field monitoring was discontinued in 2017.

Potential Impact

• Enhanced playa recharge may provide a sustainable local water resource but won't substantially change the overall water budget for the Ogallala. The TWDB Groundwater Availability Model for the Southern High Plains estimated total recharge at 1,032,905 acre-feet in 2000; recharge enhancements at the 3,000 wettest playas might gain 40,000 to 80,000 acre feet per year.
• The 200,000 acre feet of water collected annually by Texas playas represents less than four percent of the 5.6 million acre-feet of 2010 irrigation demand for Regions A and O.