Major Infrastructure on the Mokelumne River

Along the Mokelumne River, humans have built dams, reservoirs, and hydroelectric plants to provide drinking water, water for irrigation, and generate electricity for human activity, while balancing the state-assigned "co-equal goal" of managing water for threatened and endangered species. These infrastructure projects began in 1923, when the California State Legislature created the public utility organization East Bay Municipal Utility Distirct (EBMUD) to supply clean drinking water to the eastern portion of the San Francisco Bay Area, including Alameda, Contra Costa, and San Joaquin counties. The first major project was the construction of the 345-foot Pardee Dam in 1929, which blocks the flow of the river, causing water to collect and form a large artificial lake called Pardee Reservoir. Three long pipes, called aqueducts, transport the reservoir water 95 miles to the East Bay where it is the primary water source for 1.4 million people.

In 1950, severe rain caused a massive flood along the Mokelumne River, covering the city of Lodi with three feet of water. The Camanche Dam was built downstream of the Pardee Dam to help control flooding by limiting the amount of water that flows down the river. Pacific Gas and Electric (PG&E) has also built dams along the Mokelumne River, such as the Salt Springs Dam, which was built in 1931 to generate hydroelectric power by harnessing the energy of flowing water.

These dams disrupt the river’s ecosystem. Salmon, a keystone species in this watershed, and throughout the San Francisco Bay Delta, can’t cross dams to reach their spawning areas when swimming upstream. To help increase the salmon population, EBMUD established a fish hatchery below the Camanche Dam. Each fall season, they also release the river's flow in "cold water pulses" from the dams to assist salmon in navigating upstream. Downstream of Camanche Dam, they add gravel to the river to restore spawning habitat and create better places for fish to lay their eggs. Those salmon that return to the hatchery are caputred and the eggs are harvested to farm the next generation.