Colusa National Wildlife Refuge is one of five refuges in the Sacramento Refuge Complex located in the Sacramento Valley of north-central California. The refuge is about 70 miles north of the metropolitan area of Sacramento.

The 4,507-acre refuge primarily consists of intensively managed wetland impoundments, with some grassland and riparian habitat. The Sacramento Valley is one of the most important wintering areas for waterfowl in North America. Colusa Refuge typically supports wintering populations of more than 200,000 ducks and 50,000 geese.

Wetland impoundments are intensively managed to provide optimal habitat for the dense concentration of wintering waterfowl, as well as habitat for resident wildlife and spring/summer migrants.

The grassland habitat supports several populations of endangered and sensitive species of plants. The refuge is a stronghold for populations of the endangered palmate-bracted bird's-beak and the threatened giant garter snake. About 25,000 visitors come to the refuge each year for wildlife viewing and 4,000 come to hunt waterfowl and pheasant.

From Williams, exit Interstate 5 at Williams. Travel approximately 6 miles to graveled Ohair Rd. Travel south on graveled Ohair Road to the refuge entrance.

Water levels are manipulated to encourage or discourage vegetation species, create suitable depths for a variety of wildlife, and minimize mosquito production. Due to the levee systems on local rivers that prevent natural flood events, most refuge wetlands are largely "artificial." Water is delivered through local irrigation districts.

Significant quantities of vernal pool-alkali meadow habitat are naturally filled with rainwater or extreme flood events and provide some of the most diverse native flora and fauna in the Sacramento Valley. The refuge's annual habitat management plan sets objectives and directs management activities, prioritizing work on approximately 30 habitat units.

The plan includes floodup and drawdown dates, vegetation manipulation required, levee repairs, special management considerations, and other tasks required to meet refuge objectives. Standardized ground and aerial wildlife surveys and vegetation surveys are conducted regularly throughout the year to inventory populations and document habitat use.

Each year units are evaluated by how well they met habitat and wildlife use objectives. The manager, biologist, and field crew revisit each unit annually, using the wildlife and habitat data to assess the previous year and to formulate the upcoming year's plan.

Various combinations of burning, grazing, herbiciding, and water management are used to control exotic or rank vegetation. These data are stored in a computer database where they can be accessed, analyzed, and reported. Research is encouraged, and staff are involved with initiating and conducting studies that have direct applications to management.