Projected changes in dust emissions and regional air quality due to the shrinking Salton Sea

Abstract

The Salton Sea lake level in California is expected to transition in 2018 from a period of gradual decline to a new era of rapid decline that will expose about 40% of the year 2000 lakebed to wind erosion by 2030. The newly exposed Playa substrate can emit large amounts of particulate matter (PM) and thus degrade regional air quality. We use the Weather Research Forecast model (WRF-Chem) to estimate changes in dust aerosol emission and distribution in the Salton Sea region from 2000 to 2030. First, we evaluate simulations of present day wind speed, mineral dust emission, concentration, and optical depth over the region. WRF-Chem at 4 km spatial resolution satisfactorily reproduces the present-day spatio-temporal pattern of dust emission. With an estimated 38% exposure of the Salton Sea by 2030, the domain-averaged PM10 in the 2 × 2 degree domain enclosing the Sea increases on average by 11% and by nearly a factor of ten in localized source areas. The simulated increases in dust emission are consistent with earlier empirical estimates although our estimates are comparatively lower. Our regional model provides more spatially detailed and quantitative attribution of the projected air quality degradation. For example, our model suggests that newly exposed playa emissions will emanate more from the southwest than southeast side of the lake, even though most of the new playa will be on the southeast side. These results may inform decisions that affect trade-offs between environmental quality, human health, and water-use issues in the Salton Sea region.