Impact of rain events on water quality in the Lower Calaveras River Watershed

Many waterways in California’s Central Valley have water quality impairments resulting from urban and agricultural impacts. The Lower Calaveras River (LCR), which flows through the University of the Pacific’s campus, is no exception. The LCR is a stretch of the Calaveras that starts at New Hogan Dam and ends at the confluence with the San Joaquin River. The LCR provides drinking and irrigation water to the city of Stockton and surrounding communities via the Stockton East Water District, as well as a habitat for numerous aquatic species. The goal of this study was to measure water quality parameters at multiple locations in the LCR to determine potential sources of impairment to the watershed. Samples were collected during three surveys – one prior to the first major storm and two immediately following major precipitation events during winter 2006-2007. In situ measurements of temperature, conductivity, and pH, along with field measurements of turbidity were collected at each site. In addition, samples were collected for E. Coli and fecal coliform analysis at the University of the Pacific. Results indicate there is a positive correlation between turbidity and bacteria levels. Cosgrove Creek, a tributary leading into the LCR immediately downstream of New Hogan Dam, is impaired with the highest levels of bacteria. In addition, two smaller un-named tributaries also contributed significant levels of bacteria to the LCR. Ongoing studies include an investigation of the relationship between nutrient levels and bacteria, as well as the relationship between land use and water quality in LC