Major modifications of California's freshwater sources began with the discovery of gold on the western slope of the Sierra Nevada, in 1848. Early prospectors looked for gold by agitating ore and stream water in a pan and watching for the heavier gold particles to separate from sand and mud and settle at the bottom of the pan. By the mid-1850s, however, more water-intensive methods of extracting gold were used.
Hydraulic mining involved aiming high-pressure water hoses at the side of the mountain to clear away topsoil, and filtering out the gold from the gravel and debris that washed down. This technique was very destructive environmentally.
Sand, silt, and gravel from the mines clogged the Sacramento and other rivers, causing damaging floods and making navigation by steamboat nearly impossible. Farmers whose land had been ruined began seeking redress from the courts. In 1884, a judge from the US 9th Circuit Court issued an injunction against all hydraulic mining in the state.