Playas are small (usually circular), shallow, clay-bottomed depressions of aquifer-recharging wetlands occurring in the Great Plains region that are formed through a combination of wind, wave, and dissolution processes, with each playa existing within its own watershed.Playas of the Great Plains receive water only from precipitation and runoff, but water is lost through evaporation, transpiration, and recharge.The vast majority of playas occur on the Great Plains from Wyoming and Nebraska to Texas and New Mexico.
Playas, occurring primarily in semi-arid to arid environments, provide irreplaceable habitat for native plants and animals, including migratory birds.They are essential for the health and maintenance of biotic diversity throughout the Great Plains.By having erratic cycles of drying and filling, water fluctuations promote a diverse growth of herbaceous plants.Whether the plants are annual or perennial, terrestrial or aquatic, depends on how long the playa has been with or without water.
The highest density of playas occurs south of the Canadian River on the Southern High Plains…an area also known as the Llano Estacado.The Llano Estacado is one of the largest plateaus in North America covering about 82,000 sq. k (31,700 sq. mi.).It is largely a featureless landscape, but is surrounded by relatively abrupt escarpments on the west (Mescalero) and north and east sides (Caprock) varying in height from 50-200 m (160-660 ft.).The southern end of the Llano gradually fades into the Permian Basin region.The elevation of the Llano declines from about 1,500 m (5,000 ft.) in the northwest to 725 m (2,300 ft.) in the southeast.
Playas are the most ubiquitous water feature on the Llano Estacado with a density averaging 1/26 sq. k (1/sq. mi.).The wetland density can be best appreciated as seen from the air after a rain.The exact number of playas on the Great Plains is not known, but it is in excess of 25,000.
The playa region from western Nebraska to the southern end of the Llano Estacado is considered to be a short-grass prairie.The uncultivated uplands and playa watersheds are dominated by grasses like the gramas (Bouteloua spp.) and buffalo grass (Buchloedactyloides) with a scattering of wheatgrass (Agropyron spp.), three-awns (Aristida spp.), yuccas (Yucca spp.), and prickly-pear cactus (Opuntia spp.)Where sandy soils predominate, mixed stands of sandsage (Artemesiafilifolia), sand shinnery oak (Quercushavardii), bluestem grasses (Andropogon spp.), grama grasses, and yucca occur.
Adapted from Playas of the Great Plains by Loren M. Smith, University of Texas Press, 2003.