Risk assessment of point and nonpoint source pollution on water resources along the Santa Ana River (California)

Water pollution is among one of our greatest concerns, as we now forward into the 21st century. In this research, Non Point Source Pollution (NPSP) and Point Source Pollution (PSP) risks on water resources caused by environmental sensitive sites along the Santa Ana River are assessed with GIS software. The Santa Ana River watershed in Orange County was divided into 27 sub zones. At each sub zone, scores were given to each site and geology types and then their total score, site-average and number of sites in each zone are calculated. The high risk areas are determined with consideration of groundwater flow and other features of the area. Large numbers of sites, permeable geological types, proximity to groundwater aquifer attributes high risk. Though direction of groundwater flow towards the Santa Ana River and the extent of site concentration play important roles for the impacts, the impacts depend on how easy pollutants are attenuated and dispersed.