ESTIMATION OF GROUNDWATER EVAPORATION AND SALT FLUX FROM OWENS LAKE, CALIFORNIA, USA

Groundwater evaporation and subsequent precipitation of soluble sails at Owens Lake in eastern California have created one of the single lar gest sources of airborne dust in the USA, yet the evaporation add salt Aux have not been fully quantified. In this study, we compare eddy co rrelation, microlysimeters and solute profiling methods to determine t heir validity and sensitivity in playa environments. These techniques are often used to estimate evaporative losses, yet have not been criti cally compared al one field site to judge their relative effectiveness and accuracy, Results suggest that eddy correlation methods are the m ost widely applicable for the variety of conditions found oa large pla ya lakes. Chloride profiling is shown to he highly sensitive to therma l and density-driven fluxes in the near surface and, as a result, appe ars to underestimate yearly groundwater evaporation. Yearly mean groun dwater evaporation from the playa surface estimated from the three stu dy areas was found to range from 88 to 104 mm year(-1), whereas mean e vaporation from the brine-covered areas was 872 mm year(-1). Uncertain ties on these mean rates were estimated to be +/-25%, based on compari sons between eddy correlation and lysimeter estimates, On a yearly bas is, evaporation accounts for approximately 47 x 10(6) m(3) of water lo ss from the playa surface and open-water areas of the lake, Over the p laya area as much as 7.5 x 10(8) kg (7.5 x 10(5) t) of salt are annual ly concentrated by evaporation at or near the playa surface, much of w hich appears to be lost during dust storms in the area. (C) 1997 Elsev ier Science B.V.