Factors affecting regionwide water quality of San Diego County watershed

Includes bibliographical references (p. 59-63).San Diego Coastkeeper ("Coastkeeper"), a local grassroots nonprofit organization, has a volunteer-based water quality monitoring program that collects monthly stream samples from over 50 sampling sites within 9 of the 11 watersheds in the San Diego Region. Coastkeeper tests the samples for nutrients (NH???, NO???-, PO???), fecal indicator bacteria (E. Coli, enterococci, total coliforms), metals (Cd, Cr, Cu, Ni, Pb, Zn), and water chemistry (conductivity, dissolved oxygen, pH). These measurements are compared to the San Diego Basin Plan's limits to see if any water quality parameters exceed the standards. As of 2008, there are 274 water segments in the San Diego County that do not meet water quality standards. The Regional Water Quality Board reviews water quality data every two years to update the 303(d) list of impaired waterbodies. Coastkeeper is one of the organizations that assist in providing data to the public, local stakeholders, and lawmakers to make informed decisions regarding regulations. This study evaluates factors that may affect water quality from a regionwide perspective. Using the data from Coastkeeper's water quality monitoring program from 2010, this study examined the frequency of exceedances for each water quality parameter and sampling site, compared the number of water quality exceedances during the wet season (November-April) against the dry season (May-October), performed correlational statistics between rainfall amount and water quality parameters, and lastly looked at how land use types affected water quality. Overall, in 2010, San Diego region experienced a 24.4% exceedance of water quality standards. The highest frequency of exceedances was found to be ammonia and enterococci, with San Dieguito and Otay watersheds as having total number of exceedances greater than 40%. In addition, there were higher levels of exceedances during the wet season than during the dry season. Significant associations between rainfall amount and water quality parameters were higher in metals. There was a significant relationship found between agriculture land use type and nitrate