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A Thirsty Land, California

created Feb 25, 2016 02:21 PM

A brief history of drought and water use in an arid state

by Shelley Brooks

After four consecutive dry years, over 40% of California is experiencing what is known as an exceptional drought. California, like most states west of the 100th meridian, is arid, with average annual rainfall around 30 inches or below. The term “average,” however, is misleading, as rainfall varies dramatically not only from the northwest corner of the state to the southeastern desert, but from one year to the next. And in years with little snowfall or rain, drought strikes hard against California, the state that supports the largest population and economy in the country. Water is the life source for California, and there is almost never enough of it. As the population increases, and climate change brings more unpredictable weather patterns, long-term drought becomes an even more likely scenario. The mega-drought is not unknown in this region; tree rings suggest that multiple dry periods lasting 10-20 years have occurred over the past 1000 years.

California’s rich agricultural sector is deeply implicated in the drought’s impact. The crops and animals grown for market consume a majority of California’s developed water supply. With water allocations reduced or eliminated during the drought, farmers have faced difficult choices, sometimes deciding to lay fallow fields, plow under crops, and transition to less water-intensive crops. In recent years, with only a fraction of the average snowpack (which, through rivers, provides a significant portion of the state’s water), farmers and cities are relying more heavily on groundwater. As groundwater pumping draws down the water table, some land has become unstable and simply sunk in, known as subsidence. It will take years of good rain to replenish the tapped aquifers. Ironically, dry fields are contributing to faster snowmelt by creating more dust that settles on the snow and absorbs the sun’s energy. An additional challenge is felt in the Sacramento-San Joaquin River Delta, where low river flows can allow too much saltwater intrusion from the San Francisco Bay. The Delta, which provides drinking water for 25 million residents and irrigation water for the Central Valley, must deliver fresh, not salt water to its consumers.

Governor Jerry Brown, who also presided over the state during the memorable ’76-’77 drought, declared a drought State of Emergency in January 2014, and asked Californians to voluntarily cut back on their water usage. In May 2015 the state took a historic step by mandating a 25% urban water use reduction. With some variation from month to month, Californians are currently meeting that target. Despite these dramatic developments, however, no one can claim surprise over California’s predicament. California’s aridity has long prompted extensive hydraulic engineering in an effort to overcome a limited and unpredictable water supply.

California’s earliest inhabitants recognized the scarcity of fresh water, especially during the summer growing season. Few California Native American groups practiced agriculture, but the Mojave and Yuma Indians employed basic irrigation techniques in order to grow crops in the dry Colorado Desert region. By the late nineteenth century, California farmers organized themselves into irrigation districts to try and finance the costly process of bringing water to their fields. Storing water and preventing floods during the winter rains, and channeling water during the long dry season, was too big of a task for individuals, municipalities, and even the state, thereby prompting the arrival of the federal Bureau of Reclamation in the early twentieth century. But it wasn’t until the massive work projects of the Great Depression that headway was made, when the state and federal government joined forces to create the Central Valley Project (CVP) on the heels of a six year drought. California’s rapid development during and after WWII meant that additional manipulation would be necessary to meet agricultural and municipal needs. With massive population and industrial growth in the South - the region with the lowest natural water supply - the state explored ways to bring water from the North to the thirsty South. In 1960, amidst great debate between northerners who feared loss of their local supply, and southerners who worried what the long term implications of this arrangement would be, California voters approved the State Water Project (SWP) to augment the CVP. With hundreds of miles of canals, numerous storage facilities and pumping stations, the SWP is the nation’s largest state-built water and power development and distribution system.

In short, California’s water resources have been continuously managed to accommodate a growing number of people and industries in areas that lack sufficient natural water supply. This is an impressive feat even during wet years; in dry years the challenge seems nearly insurmountable. Californians have always tapped the state’s natural resources to create abundance and opportunity, but for all their innovation and adaptation, Californians cannot increase the quantity of the water. Instead, during this exceptional drought, Californians are challenged to adjust their expectations and decrease water demands, not just to lessen the impact for the rest of this year or next, but for the inevitable droughts of the future as well.             

Visit the CHSSP Blog for a classroom activity on Sierra Nevada snowpack and local watersheds.

Image: Lake Hume, by Tim Keegan,