KNIGHTS LANDING, Calif. — Driving between her northern Central Valley rice fields with the family dog in tow, fifth-generation farmer Kim Gallagher points out the window to shorebirds, egrets and avocets fluttering across a thousand-acre sea of green flooded in six inches of water.

“People say agriculture uses so much water, but if you knew who lived in these areas and if you saw the animals taking advantage of it, you’d think there’s a lot more going on here,” Gallagher said. “This is where you’re going to find a Great Blue Heron. If you don’t want that type of bird then we shouldn’t be growing rice.”

The nearly 500,000 acres of sushi rice grown in the Sacramento Valley each year serve as the wetland habitat for thousands of migrating birds along the Pacific Coast. Yet the crop also uses more water than most, and about half of the product is exported to countries including Japan and South Korea.

Since the 1920s, farmers have grown rice in the Sacramento Valley, where old hands fly crop duster planes and rice emblems mark the county buildings. Now, due to decades-old agreements with the federal government, rice farmers like Gallagher are going relatively unscathed by unprecedented emergency water cuts to farmers this month as others fallow fields, wells go dry and low water levels imperil Chinook salmon, the native cold-water fish that play critical ecological roles and support a billion-dollar fishing industry.