Data_Sheet_1_Analysis and Classification of Stormwater and Wastewater Runoff From the Tijuana River Using Remote Sensing Imagery.pdf

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.

城市地表径流是南加州近岸海域海洋污染的首要成因。本研究聚焦于横跨美墨西南边境的提华纳河流域所引发的水质问题。该区域向近岸海域的高频排放事件涵盖暴雨径流与生活污水两类。本研究借助RapidEye、Sentinel-2 A/B及Landsat-8卫星数据，结合原位物理与生物观测数据，通过分析光谱特征差异对水羽流进行表征与分类，共划分为四大类别：暴雨径流羽流、生活污水羽流、远海/无羽流以及混合羽流（即同时存在两类羽流的场景）。可见光至近红外（Near-Infrared, NIR）波段的关键光谱差异表明：暴雨径流羽流的反射率最高（0.02~0.09），其次为混合羽流（0~0.08）、生活污水羽流（0~0.05），远海/无羽流事件的反射率最低（0~0.03）。本研究同时分析了生物物理参数，结果显示：基于遥感估算的有色溶解有机物（Colored Dissolved Organic Matter, CDOM）（0.98~2.1 m⁻¹）与浊度（12.4~45.7 FNU）中，暴雨径流事件的数值最高；原位观测的肠球菌菌落数与流速数据也呈现出较大的波动范围。本研究还发现，当某一类羽流占主导地位时，利用光谱特征开展层次聚类分析（Hierarchical Cluster Analysis）可准确区分暴雨径流羽流与生活污水羽流。本研究结果可助力优化两类羽流的输运路径解析，并推动南加州/下加利福尼亚半岛区域的近岸水质跨境监测工作。