Estimation of groundwater evaporation and salt flux from Owens Lake, California, USA

Abstract

Groundwater evaporation and subsequent precipitation of soluble salts at Owens Lake in eastern California have created one of the single largest sources of airborne dust in the USA, yet the evaporation and salt flux have not been fully quantified. In this study, we compare eddy correlation, microlysimeters and solute profiling methods to determine their validity and sensitivity in playa environments. These techniques are often used to estimate evaporative losses, yet have not been critically compared at one field site to judge their relative effectiveness and accuracy. Results suggest that eddy correlation methods are the most widely applicable for the variety of conditions found on large playa lakes. Chloride profiling is shown to be highly sensitive to thermal and density-driven fluxes in the near surface and, as a result, appears to underestimate yearly groundwater evaporation. Yearly mean groundwater evaporation from the playa surface estimated from the three study areas was found to range from 88 to 104 mm year −1, whereas mean evaporation from the brine-covered areas was 872 mm year −1. Uncertainties on these mean rates were estimated to be ±25%, based on comparisons between eddy correlation and lysimeter estimates. On a yearly basis, evaporation accounts for approximately 47 × 10 6 m 3 of water loss from the playa surface and open-water areas of the lake. Over the playa area, as much as 7.5 × 10 8 kg (7.5 × 10 5 t) of salt are annually concentrated by evaporation at or near the playa surface, much of which appears to be lost during dust storms in area.