The Delevan National Wildlife Refuge is one of six refuges in the Sacramento Refuge Complex in the Sacramento Valley of north-central California. The 5,797-acre refuge is approximately 80 miles north of Sacramento and consists of over 4,500 acres of intensively managed wetlands and 1,200 acres of uplands.

More than 200,000 ducks and 100,000 geese come to the refuge each winter. With 95 percent of the wetlands of the central valley lost over the last 100 years, waterfowl have become increasingly dependent upon the refuges of the Sacramento Valley.

The refuge supports several endangered plants and animals: giant garter snake, wintering peregrine falcon and bald eagle, breeding tricolored blackbird, and a large colony of the endangered palmate-bracted bird's beak. Resident wildlife include grebe, heron, blackbird, beaver, muskrat, black tailed deer and other species typical of upland and wetland habitats.

Approximately 7,000 people hunt on the refuge each year and an estimated 1,000 visitors observe wildlife from a primitive roadside overlook along the Maxwell-Colusa Highway.