Bennett Valley is a northwest- to southeast-trending valley in Sonoma County, California, US, approximately 1 mile (1.6 km) wide in its northwestern portion, where the southeast extremity of Santa Rosa, California is located. The axis of the valley floor slopes 40 feet (12 m) per mile (a gradient of 0.008 or 7.6 m per km) from the pinched central portion of the valley, where knolls divide the northwestern from the southeastern segment of the valley. Bennett Valley is drained by Matanzas Creek which is incised into the valley floor; an unnamed stream and Spring Creek drain into Matanzas Creek from the east side of Bennett Valley below the Matanzas Creek Reservoir. A flood-control reservoir on Matanzas Creek in the central portion of the valley collects water from the drainage of the upper portion of the valley. Precipitation in the valley varies from approximately 35 to 40 inches (90 to 100 cm) per year. The latter amount falls on Taylor Mountain, located immediately above Bennett Valley, in an outlier spur of the Sonoma Mountains sometimes called the Los Gullicos Range. Rainfall occurs primarily during winters (November to April), separated by warm dry summers.