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