Water Quality Index Score: 74, Fair (20 point improvement from 2015)
The Sweetwater watershed begins in Cuyamaca Rancho State Park in the east and collects runoff from parts of Alpine, Spring Valley, La Mesa, Lemon Grove, San Diego, National City, and Chula Vista before draining into San Diego Bay. We’re happy to report the Sweetwater River improved in several key indicators compared to our 2015 results, including ammonia and fecal indicator bacteria — although we still saw numerous exceedances of FIB throughout the year. Dissolved oxygen levels were still very low for most of the year at our site off Plaza Bonita Road, likely caused by excess organic matter being broken down by bacteria in the slow-moving water.
How to read our water quality pie charts: these handy charts are designed to give you a sense of which of the factors we measured contributed to the overall water quality score (the number in the center) for each watershed. The size/color of the pie slice gets larger/warmer with increased frequency and magnitude of deviations from good water quality standards for each indicator.