Diversion of water for urban centers
As agricultural use of water in California rose beginning in the 1850s, urban centers grew too, creating a larger demand for municipal water. Small towns located along rail routes began to grow in the Central Valley, and Los Angeles and San Francisco saw big gains in population around the turn of the century and in the early years of the 20th century.
In 1880, the population of Los Angeles was 11,000. A decade later it was 60,000. In 1900, it was about 100,000. By 1921, 1 million people lived in Los Angeles County.
San Francisco already had a population of 233,000 in 1880, and this reached about 500,000 in 1920.
The increase in urban population led city leaders to initiate projects to assure the supply of fresh water and electricity from hydropower. San Francisco and Los Angeles naturally account for two of the largest such locally controlled projects.