Evaporation from groundwater discharge playas, Estancia Basin, central NewMexico

Bowen ratio meteorological stations have been deployed to measure rates of evaporation from groundwater discharge playas and from an adjacent vegetate d bench in the Estancia Basin, in central New Mexico. The playas are remnan ts of late Pleistocene pluvial Lake Estancia and are discharge areas for gr oundwater originating as precipitation in the adjacent Manzano Mts. They al so accumulate water during local precipitation events. Evaporation is calcu lated from measured values of net radiation, soil heat flux, atmospheric te mperature, and relative humidity. Evaporation rates are strongly dependent on the presence or absence of standing water in the playas, with rates incr easing more than 600% after individual rainstorms. Evaporation at site E-12 , in the southeastern part of the plays complex, measured 74 cm over a year long period from mid-1997 through mid-1998. This value compares favorably t o earlier estimates from northern Estancia playas, but is nearly three time s greater than evaporation at a similar playa in western Utah. Differences in geographical position, salt crust composition, and physical properties m ay explain some of the difference in evaporation rates in these two geograp hic regions. (C) 2000 Elsevier Science B.V. All rights reserved.