Analysis and Classification of Stormwater and Wastewater Runoff From the Tijuana River Using Remote Sensing Imagery

Abstract

Urban runoff represents the primary cause of marine pollution in the Southern California coastal oceans. This study focuses on water quality issues originating from the Tijuana River watershed, which spans the southwest border of the United States and Mexico. Frequent discharge events into the coastal ocean at this boundary include stormwater and wastewater. This study focuses on differences in spectral features, as assessed by RapidEye, Sentinel-2 A/B, and Landsat-8 satellite data, along with physical and biological in situ data, to characterize and classify plumes into four key categories: stormwater, wastewater, open ocean/no plume, and mixed (when both types of plumes are present). Key spectral differences in the visible to NIR bands showed that stormwater had elevated reflectance (0.02 to 0.09), followed by mixed (0 to 0.08), wastewater (0 to 0.05), and open ocean/no plume (0 to 0.03) events. We also examined biophysical parameters and found that stormwater events had the highest values in remote sensing based estimates of colored dissolved organic matter (CDOM) (0.98 to 2.1 m–1) and turbidity (12.4 to 45.7 FNU) and also had a large range for in situ variables of enterococcus bacteria and flow rates. This study also finds that the use of spectral features in a hierarchical cluster analysis can correctly classify stormwater from wastewater plumes when there is a dominant type. These results of this study will enable improved determination of the transport of both types of plumes and transboundary monitoring of coastal water quality across the Southern California/Baja California region.

Turbidity and fecal indicator bacteria in recreational marine waters increase following the 2018 Woolsey Fire

“…There are various remote sensing techniques for detecting plumes. Coastal plumes exhibit differences in turbidity, color, temperature, and salinity from ambient background water that can be observed via multispectral and hyperspectral imagers, thermal infrared (TIR) radiometers, microwave radiometers, and Synthetic Aperture Radar (SAR) 71 , 72 . In the Southern California Bight, ocean color imagery from SeaWiFS 73 , MODIS 74 – 76 , and Landsat 77 have been utilized and combined with radiometers 78 , 79 and SAR 50 to delineate and track plumes.…”

The Wastewater Contamination Index: A methodology to assess the risk of wastewater contamination from satellite-derived water quality indicators

“…b bspm (440)-backscattering coefficient of suspended particulate matter (SPM). These indicators were selected considering that wastewater plumes have been previously associated with high levels of CDOM (Marmorino et al, 2010;Ayad et al, 2020) and SPM (Ayad et al, 2020). High chlorophyll-a concentration has also been observed in the wake of wastewater outfalls (Trinh et al, 2017).…”

Modeling Untreated Wastewater Evolution and Swimmer Illness for Four Wastewater Infrastructure Scenarios in the San Diego‐Tijuana (US/MX) Border Region

“…However, with rainfall, diversion is often suspended due to issues with Tijuana infrastructure allowing wastewater to enter the Tijuana River (ARCADIS, 2019). Plumes from the TJRE can hug the shoreline or extend km offshore (Lahet & Stramski, 2010; Warrick et al., 2007) as a mixture of runoff and untreated wastewater (Ayad et al., 2020). TJRE plumes can impact the entire San Diego Bight particularly during winter when rainfall is more likely to occur (e.g., Kim et al., 2009).…”