Owens Valley Diversions

In the year 1913, the City of Los Angeles completed construction of the Los Angeles Aqueduct, the LAA. The LAA reached 300 miles north to the Owens Valley. (You've seen the aqueduct's location in Figure 4.1 of the book.) The LAAi s shown along side of the other major aqueducts of California in the map to the right. The City looked to the Owens Valley for water because its growing demand was about to exceed the supply from local wells. In the year 1940, the LAA was extended further north to reach into the Mono Basin. And in the 1970s, a "second barrel" of the aqueduct was constructed to increase the delivery capability of the system. The LAA is designed to collect diversions from the streams of the eastern slope of the Sierra Nevada. The stream diversions are combined with groundwater pumping in the Owens Valley to provide around 370 KAF/yr of supply in a year with average weather. (Total delivery is around 470 KAF/yr counting the diversions from the Mono Basin.)

Aqueducts in California (courtesy of the Metropolitan Water District)

The Owens Valley supply could be much larger in a wet year. In a particularly wet year, large diversions could go a long way toward supplying all of the City's demand. (The demand might be down by around 10% in a year with wet weather.). The City could find itself in the enviable position of reducing purchases from the MET and the need to pump from local wells. In particularly wet years, the pumping would be much less than ground water recharge in the key aquifers of southern California.

Owens Valley water is an extremely valuable source of water to the City because it is cheap and it is clean. The water flows by gravity the entire way to Los Angeles, allowing some electric generation in route. The water is extremely clean, so it may be mixed with more saline water in other aqueducts to meet the City's standards for water quality.

The future of Owens Valley Diversions is somewhat uncertain. (The City's rights could be reduced, for example, by litigation to reduce ground water pumping in the Owens Valley. ) Under California's Urban Water Management Planning Act of 1983, the LADWP is required to make it's best assessment of the water supplies. The LADWP's first response to the 1983 planning act was its 1985 long term plan -- the City of Los Angeles Urban Water Management Plan (LADWP 1985). The 1985 plan expected that the LAA could continue to deliver 470 KAF/yr, the amount depicted in the drawing. Later, in their 1991 Plan, the City reduced it's long run expectation for the LAA to around 380 KAF/yr under average weather conditions.