The principal flood protection facilities on the tributaries of the Russian River comprise the Central Sonoma Watershed Project, which was constructed by Sonoma Water in cooperation with the U.S. Department of Agriculture, Soil Conservation Service (now called the Natural Resource Conservation Service or NRCS). The work plan for this project was completed in 1958 and various components of this project were constructed over the ensuing 25 years. Project components included the construction of floodwater retarding structures and the straightening, shaping, and stabilization of waterways. The project alleviates flooding in the Santa Rosa urban area.
The Central Sonoma Watershed project includes flood protection reservoirs that were built in the late 1960s to reduce flooding in the Santa Rosa area. These reservoirs are:
Santa Rosa Creek Reservoir (also known as Spring Lake)
Matanzas Creek Reservoir
Piner Creek Reservoir (on Paulin Creek)
Brush Creek Middle Fork Reservoir
Spring Lake was constructed between 1961 and 1964 as a flood protection reservoir by Sonoma Water. The project, which consists of three steel and concrete dams, spillways, channels, and flow regulators and represents one of Sonoma Water's most ambitious flood protection projects, diverts floodwaters from Spring Creek and Santa Rosa Creek into Spring Lake, alleviating much of downtown Santa Rosa's flooding. The project is designed to accommodate water equal to a 100-year flood (in other words, a storm that, based on past records, has a 1 in 100 - or 1 percent - chance of occurring in any year.) Only once since the lake's construction, in 1986, has flooding been so severe as to exceed Spring Lake's capacity.
In 1974, Sonoma Water began plans to develop the land surrounding the reservoir into parkland. Today, Spring Lake Park is one of the most popular recreation areas in Sonoma County. The park's 320 acres accommodate a 72-acre lake, a 3-acre swimming lagoon, and miles of walking, hiking, and horseback-riding trails. The park also includes a visitors' center, campsites, picnic areas, and boating facilities. Spring Lake Park is operated by the Sonoma County Regional Parks Department under a contract with Sonoma Water.