Kesterson Reservoir, now within the San Luis National Wildlife Refuge in California’s San Joaquin Valley, was built in 1971 as part of the San Luis Drain and became its temporary end point after the larger project was halted in 1975. Once used by migratory waterfowl, its evaporation ponds later received saline agricultural drainage rich in selenium derived from Coast Range sediments. Evaporation concentrated the contamination, which moved through the food web and caused severe harm to birds, fish, and other organisms, drawing national attention in the 1980s. Closed in 1985, the site underwent decades of remediation and remains a major example of the environmental dangers of irrigation drainage.