At times during the winter and early spring it looks like a vast inland sea between Sacramento and Davis. This is the Yolo Bypass, which shunts Sacramento River floodwater around the state capital during high flows. You drive over the bypass on a three-mile-long elevated stretch of Interstate 80 known as “the Causeway” (the Blecher-Freeman Memorial Causeway). The bypass is also the site of a lot of innovative fish and wildlife work.

From late fall through winter you can see thousands of ducks, geese and other waterfowl winging over the bypass’s flooded rice fields and the restored wetlands in the Vic Fazio Yolo Basin Wildlife Area. The Central Valley of California is one of the...