In 1913, the City of Los Angeles Department of Water and Power (LADWP) turned the gates and diverted the water from the Owens River into the recently completed Los Angeles Aqueduct. The original Intake structure is still in use.
In 1905, the City of Los Angeles, through William Mullholland, the head of LADWP, had identified the Owens River as a new, reliable source of water for the growing city. Original land purchases in the Owens Valley by representatives of the city were sometimes confused with an effort by the Bureau of Reclamation, which was also in the area trying to locate a dam site. When it became openly known that LA was buying water rights and land in order to divert the water down south, the conflict reached the desk of President Theodore Roosevelt. Citing "the greatest good for the greatest number," Roosevelt allowed Los Angeles to proceed with its water plans and told the Bureau of Reclamation to stop its efforts in the valley. Roosevelt did, however, designate some land in the area as a national forest, a move that created what is now the Inyo National Forest.
After construction of the 200-plus mile aqueduct, the water started flowing out. However, in the mid-1920s, Owens Valley residents used dynamite to destroy parts of the aqueduct, and famously "occupied" the Alabama Gates for several days. The local protests eventually faded away as the Depression helped Los Angeles find "willing sellers" for Owens Valley land and water. The city's thirst continued to grow, especially after WW II, so it bought water rights in Mono County, and began diverting that water as well, which started the slow decline in the water levels of Mono Lake. In the 1970s, new state and federal environmental laws provided a mechanism for groups, governments and organizations to try and limit the environmental damage caused by groundwater pumping and other water-gathering activities. The lawsuits were successful, often after decades of legal battles, and now Mono Lake is protected. With a nudge from the judge, Inyo County and LADWP have been trying work together to both protect the environment and provide a stable supply of water to LA.
Re-watering of the Lower Owens River and completing dust-control measures on the Owens Dry Lake are just two of the largest mitigation measures being undertaken in the Owens Valley.