MISR Identification of Atmospheric and Surface Changes in the Salton Basin, 2000-2013

Compliance with the Quantification Settlement Agreement limits the volume of agricultural runoff flowing from the Alamo River to the Salton Sea in Southern California. By 2017, due to the discontinuation of mitigation water, the evaporation of the Salton Sea – an endorheic basin measuring 974 sq. km -- will be noticeably accelerated, aggravating the recession of the shoreline which will allow transport of toxic dust (containing trace elements) to the neighboring communities of Imperial Valley and Coachella Valley. This creates a high concern for the declining, below-standard air quality of the basin, establishing the need for a statistical study detailing the dominant factors influencing the spread, duration, magnitude and frequency of toxic dust events in the region. Satellite remote sensing is a productive means of monitoring environmental change, as the placement of instrumentation in Earth orbit provides opportunities to obtain wide areal coverage and frequent revisits of the same region over a long period of time. We characterize conditions in the Salton Basin using JPL's Multi-angle Imaging SpectroRadiometer (MISR) instrument, one of five sensors flying aboard Terra satellite since 2000. We developed an automatic method to monitor changes in the surface area of the Salton Sea in the quantitative manner using MISR imagery at 275 m spatial resolution. This technique allows us to quantify shoreline recession of 3.3 km2 per year with nearly linear trend. Overall MISR observes 43.2 km2 (4.7% of the total) decrease of the Salton Sea water area over 13 years. If this trend continues, the Salton Sea is likely to lose an additional 23.3 km2 (7.2% of the total) by 2020. MISR aerosol product from the Salton Sea region was used to assess whether or not regional aerosol and dust loadings had changed over 13 year due to this observed decrease in the water area. While Aerosol optical depth (AOD) and surface PM2.5 do not change significantly over 13 years, the MISR dust fraction shows statistically significant positive trend in the last decade. A manual analysis of 1,520 images captured within this same timespan also shows prevalence of strong dust events in the last five years.