New Mexico Geological Society Annual Spring Meeting — Abstracts

The Estancia Basin playa complex is located in central New Mexico. During the late Pleistocene (~12,000 years BP) a large perennial lake evaporated, leaving a flat valley floor. In the mid-Holocene about 80 deflation basins were excavated into the valley floor and these basins are now occupied by wet playas. Deflation ofthe playa basins coincided with a drop in the water table elevation to ~10 meters below the old lake floor. Following deflation, the playa basins have accumulated up to ~2 meters of sediment and playa surfaces are generally wet or covered by shallow water during part of the annual cycle.

Our research is attempting to study atmospheric and hydrologic interactions to develop an understanding of the climatic controls on changes in water level and sedimentI accumulation in the Estancia Playa complex as a step toward developing a basin model to help investigate controls on water levels in the basin extending into the late Pleistocene.

Currently, we have installed three meteorological stations. Two of these stations are located on playa floors in basins at the center and near the margin of the playa complex. The other station is installed in a vegetated area adjacent to the central playa. We have also installed several transects of piezometer nests in the same playas in order to determine rates of groundwater discharge into the playas and compare hydrologic and atmospheric estimates of evaporation. The meteorological stations record a number of observations on twenty-minute averages. Bowen ratio calculations and precipitation measurements reveal that rates of evaporation are significantly influenced by the amount ofstanding water on the playa surface as well as the amount of cloud cover. Comparison of data obtained from the three stations shows a high degree of coherence between meteorological variables at the different sites and also a close relationship to regional observations.