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Characterization of Water Quality in the Los Angeles River





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The Los Angeles River is one of the most highly modified systems in the world. Dramatic modifications have successfully reduced flooding and prop- erty damage, but little of the engineered design has incorporated water quality improvements. The goal of this study was to identify sources of potential pollut- ants and characterize water quality along the river's seven reaches during dry weather. The three primary sources of potential pollutants included water recla- mation plants (WRPs), major tributaries, and storm drain outfalls. In addition, the use of volunteers as a mechanism to collect data at large spatial scales, where tremendous labor is required over short periods of time, is evaluated. The three WRPs discharged the majority (72%) of the volume flowing in the Los Angeles River during this study. Likewise, the three WRPs discharged the highest concentrations and greatest mass emissions of nutrients including nitrate, nitrite, ammonia, and total phosphate. In contrast, 66 flowing storm drains and 6 flowing tributaries had the highest concentrations and mass emissions of bacteria including total coliform, E. coli, and enterococcus. Water quality in the Los Angeles River responded to inputs of potential pol- lutants. Levels of nutrients were generally low upstream and downstream of the WRPs (WRPs (approximately 6 mg/L ammonia). Concentrations of bacteria were gen- erally high upstream and downstream of the WRPs (ca. 10 4 MPN/100 mL E. coli), but were lowest in the immediate vicinity of the WRPs (ca. 10 2 MPN/100 mL E. coli).