City of Santa Rosa > Departments > Water > Water > Water Quality > Sonoma County Water Agency Reports


The City of Santa Rosa primarily receives water from the Sonoma County Water Agency (SCWA) through its wells near the Russian River and conveyed through their aqueduct system. The SCWA is Sonoma County’s wholesale water supplier to most of the cities in central and southern Sonoma County. The SCWA water supply is not drawn directly from the Russian River but through water wells and specialized wells commonly called “radial collectors” near the river. These wells are able to draw large amounts of water from the loose gravel under the river to provide high-quality, filtered water to residents in Sonoma and Marin Counties. The SCWA treats the water with gas chlorine for bacterial disinfection, and sodium hydroxide (also known as caustic soda) to adjust the pH before it is delivered to Santa Rosa. The pH treatment is necessary to comply with Environmental Protection Agency (EPA) regulations on the copper content in drinking water. Raising the pH helps minimize the leaching of copper and other metals from the distribution pipe into the drinking water. The SCWA transports the water through huge water aqueducts with supply reservoirs along the way. The SCWA has a water supply interactive map that explains the entire water system at: http://www.scwa.ca.gov/water-system/.


The City of Santa Rosa operates two drinking water wells in east Santa Rosa during the high use summer and fall periods. The two wells have a combined output of 2.5 million gallons-per-day. Sodium hypochlorite or common bleach is added to Santa Rosa’s well supply for disinfection. The wells are very deep and have an average temperature of 80°F. Manganese exceeds secondary standards so a filter vessel removes it before it is delivered to customers.  

The Russian River watershed system has three main reservoirs, Lake Pillsbury, Lake Mendocino, and Lake Sonoma which replenishes the aquifer supplying the SCWA well systems located near Forestville. The natural filtration below the river removes organic material and turbidity leaving high-quality drinking water for over 600,000 residents of Sonoma and Marin counties.

Each year, SCWA provides detailed sampling results for each of their water sources. Santa Rosa uses this sampling data to produce the federally mandated "Consumer Confidence Report" which Santa Rosa calls the Water Quality Report. Santa Rosa also utilizes local water well supplies that also must be analyzed. Those results are also included in their Consumer Confidence Report. Santa Rosa's Water Quality Reports are at the link to the left. Below are the last seven years of sampling data from SCWA and from Santa Rosa's Farmers Lane Water Treatment Plant: