What environmental issue was revealed by the discovery of dead and deformed waterfowl at Kesterson Reservoir in 1983?

The discovery of dead and deformed waterfowl at Kesterson Reservoir in 1983 highlighted a significant environmental issue related to water pollution from agricultural drainage. This situation emerged as a result of agricultural runoff containing high levels of selenium, a toxic element that accumulates in the environment through agricultural practices, particularly in the context of irrigation in arid regions like California's San Joaquin Valley.

The water that flowed into Kesterson Reservoir was a mix from farm fields, carrying pesticides, fertilizers, and various contaminants. Over time, the evaporation process concentrated these pollutants, leading to dangerously high levels of selenium in the water and sediment. Selenium is particularly harmful to wildlife, especially birds, as it can cause deformities and increased mortality rates. This incident raised awareness about the effects of agricultural practices on ecosystems, driving regulatory changes and promoting more sustainable farming methods to protect water quality and wildlife.

Understanding this case is crucial, as it exemplifies the broader impacts of agricultural pollution on water resources and wildlife, a significant issue within California's complex water management landscape.