Analysis of long-term (2002-2020) trends and peak events in total suspended solids concentrations in the Chesapeake Bay using MODIS imagery

Water quality monitoring programs have been widely implemented worldwide to monitor and assess water quality and to understand its trends. However, water quality analysis based on point-source field observations is difficult to perform at large spatial and temporal scales. In this paper, a fully automated Google Earth Engine (GEE) application algorithm was developed to estimate the total suspended solids (TSS) concentration in the Chesapeake Bay based on the Moderate Resolution Imaging Spectroradiometer (MODIS) Terra imagery. Combining long-term archived satellite data (2002-2020) with field observations, the concentrations and spatiotemporal patterns of TSS in the bay water were evaluated. Time series analysis showed a statistically significant decreasing trend in TSS concentration between 2002 and 2020, suggesting that the sediment concentration in the bay has gradually been decreasing over the last two decades. The decreasing trend was observed in 49 out of 60 segments of the bay, implying that substantial progress has been made toward attaining the Chesapeake Bay water quality standards. Based on the monthly TSS analysis, 12 major peak events of TSS were identified in the Chesapeake Bay, which coincided with extreme winter blizzards and summer hurricane events. The GEE application and the results presented herein complement the existing monitoring program in attaining the water quality standards of the bay.

Automated summary

Water quality monitoring programs are widely implemented globally to monitor water quality and trends, but analyzing based on point-source field observations is challenging at large scales. This study used a Google Earth Engine algorithm to estimate TSS concentration in Chesapeake Bay using MODIS Terra imagery. Results showed a decreasing trend in TSS concentration over the past two decades, with major peak events coinciding with extreme weather events. The application complements existing monitoring programs to attain water quality standards.