Southern Subbasin Overview
The Southern Subbasin is composed of a watershed area that begins at the northern end of Little Lake Valley just north of Willits, and extends southward to include the headwaters of Outlet Creek. This is the largest of the Outlet Creek subbasins as its 64 square miles (40,737 acres) represents 45% of the Outlet Creek Basin area. Elevation ranges from 1,310 feet in the lower valley to 2,400 ft.
Willits, with a population of 4,888 people (U.S. Census 2010), is the only significant community in the subbasin. The overall population of the subbasin is estimated at 11,115 residents. Approximately 98% of the land is privately owned. Prominent land uses include: grazing, ranching, timber production, and small and large rural residential and commercial properties.
Chinook and coho salmon and steelhead trout spawn and rear in this subbasin. The coho salmon populations present represent the furthest inland spawning run remaining in California, which is 160 miles from the Pacific Ocean. The average precipitation is 45 inches a year which mainly falls as rain. Rainfall and subsequent stream flows are impounded by six dams located in this subbasin. Impounding flows inhibit the upstream adult Chinook and coho salmon spawning migration to Outlet Creek. Similar to the other subbasins, natural flow conditions are severely reduced by groundwater extraction and other dewatering activities causing some tributaries to run subsurface during the late summer and early fall. This has led to juvenile salmonid stranding and mortality.