Origin and Development of Playa Basins, Sources of Recharge to the Ogallala Aquifer, Southern High Plains, Texas and New Mexico

More than 20,000 playa basins have formed on the Southern High Plains of Texas and New Mexico. These small, internally drained, roughly circular to oval depressions are economically important because they collect runoff and focus recharge to the Ogallala aquifer, which is the primary domestic and agricultural source of water on the Southern High Plains.Across the High Plains, playa basins vary greatly in size and depth, both of which, we found, are largely controlled by the texture of the sediments that host playa basins. For example, for equal amounts of rainfall, runoff is greater on clayey soils than on loams. Larger playa basins are forming in areas of poorly permeable clayey soils because of increased potential for runoff and fluvial erosion. In areas of higher runoff more sediment is removed from basin slopes and carried to the playa basin floor, where it is available for deflation.Playa basins formed as a result of the interaction of geomorphic, pedogenic, hydrochemical, and biologic processes. Evidence of eolian processes includes lee dunes on the east side of certain playa basins, which are composed of sediment deflated from the playa basin and straightened shorelines on the east and south margins of many playa lakes. Evidence of fluvial processes includes centripetal drainage that feeds fan deltas at the playa margins. The roughly circular shape of these basins results primarily from centripetal drainage and erosion and transport of sediment to the basin floor. Other processes that may have played secondary roles in the development of playa basins include subsidence induced by dissolution of soil carbonate or of deeply buried Permian salt and eluviation or piping of surface sediments. Destruction of stabilizing vegetation by periodic flooding and of soil crusts by grazing animals probably promoted deflation of playa sediments.Playa basins are stable landforms, which, once initiated, tend to persist in the landscape. The interbedding of Blackwater Draw and playa sediments indicates that playa basins were developing as the Quaternary Blackwater Draw was being deposited. The absence of Miocene-Pliocene Ogallala caprock calcrete beneath parts of some playa basins may indicate that as early as late Ogallala time these playa basins began to develop as solution pans on the caprock calcrete.Development of playa basins and the long-term stability of these landforms result partly from the difference in rates of sediment accumulation in upland areas versus playas. A stable landscape prevailed on the High Plains uplands throughout much of the Quaternary and perhaps late Tertiary, preserving both eolian sediments and soil CaCO3 in interplaya areas. During the same period, although playas accumulated lacustrine sediment, relatively small amounts of eolian and deltaic sediment, and small amounts of pedogenic CaCO3, they were subject to deflation. As a result, playa basins were enlarged (deepened) relative to surrounding uplands partly by more rapid vertical accretion of sediment and soil carbonate on uplands.The purpose of this report is to (1) present new and significant data on playa basin morphology and developmental processes, (2) critically review current hypotheses of playa basin origin and development, and (3) describe a model of the origin and development of playa basins
Thomas C. Gustavson
Vance T. Holliday
Susan D. Hovorka

Gustavson, T. C., Holliday, V. T., and Hovorka, S. D., 1995, Origin and Development of Playa Basins, Sources of Recharge to the Ogallala Aquifer, Southern High Plains, Texas and New Mexico: The University of Texas at Austin, Bureau of Economic Geology, Report of Investigations No. 229, 44 p.

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The University of Texas at Austin, Bureau of Economic Geology
Report of Investigation