Where Does Your Water Come From?
In California, chances are the water coming out of your tap has made an impressive journey. Our state is justly famous for its spectacular natural beauty, abundant sunshine, fertile farmlands, and enterprising communities. These characteristics have combined to make California one of the most productive places on earth. The critical feature that allows this modern miracle to happen involves moving water from where the rain falls to where the water is needed in a reliable and sustainable way. Large parts of California are semi-desert year round, and almost everywhere our climate is hot and dry during the long summer when water is in highest demand.
Without the development and innovative management of the state’s limited water resources, the story of California’s success would be very different, for water is truly vital to our economy. Figuring out ways to spread this already limited resource ever farther, to serve everyone adequately — including homeowners, farmers, businesses, industry, fisheries, and the environment — has always been difficult. And the challenges are growing yearly, as our population increases. If we don’t continue to invest in the system and strive to conserve, it’s pretty clear that the place we call home is headed for serious shortages. (For more on this see pages 12 and 13.)
How have we managed so far? Through developing a system of dams, reservoirs, aqueducts, and pipelines that carry vast amounts of water from where it is collected to the places where it's most needed. Where does your water come from? It depends. The water’s journey could be short. But more likely than not, some of it has traveled many miles, and sometimes even hundreds.
Starting Points
To understand how it all works, let’s start with the water itself. Some of the water we consume is groundwater. Groundwater is the accumulation of precipitation that is hidden in the rocks, sands and gravels below the surface. Wells are drilled and pumping stations built to raise the water to the surface. These underground reservoirs, also known as aquifers, are found only in select areas. They must be managed carefully so the amount of water pumped out does not exceed the amount recharged over time. (A strategy called water banking is used in some areas to recharge underground storage basins using water transported from areas with water surpluses.) Groundwater typically accounts for about 40 percent of statewide water use in average years. The percentage can be considerably greater in drought years when surface water is in short supply. Surface water refers to water in rivers and streams that originates as rain and snow. About two-thirds of the precipitation we receive evaporates into the air, soaks into the ground, or is absorbed by vegetation. The remainder runs down hillsides to lakes, ponds, rivers and streams that lie within natural basins called watersheds. Some of the runoff flows into wild and scenic rivers or environmentally sensitive estuaries and eventually makes its way to the ocean. The rest is considered California’s “usable” water supply, or what is actually collected and stored in the state’s vast water storage and delivery system.
In normal years as much as 75 percent of California’s usable water falls as snow and rain in the northern third of the state between November and March, mostly on the western slopes of the Sierra Nevada mountains. Climate change is likely to add a new variability to this pattern, however. Another significant portion of the state’s surface water comes from the Colorado River, which originates in the Rocky Mountains and traverses a number of other mountainous states to the east. As much as 80 percent of California’s water demand is in the southern two-thirds of the state where very little surface water is found naturally.
To remedy the existing inequities between supply and demand, federal, state and regional authorities have built perhaps the most complex water storage, water transport, and flood management system found anywhere. Major regional projects serve Los Angeles, San Francisco and the East Bay. Dozens of local projects serve people around the state. Three of the largest water projects in the state that serve multiple cities and agricultural areas include:
The Central Valley Project (CVP) runs 450 miles through a vast oblong valley that begins with Lake Shasta in the north and extends to Bakersfield in the south. The CVP captures and conveys water from the state’s largest river, the Sacramento. Farther south, the San Joaquin and several other smaller rivers contribute to the system. Work began on the CVP in the 1930s and was originally conceived as a relatively modest state project. When financing failed, the CVP was taken over by the federal Bureau of Reclamation. Construction grew to include 18 dams and reservoirs, 500 miles of canals and aqueducts, 11 hydroelectric power plants, and three fish hatcheries. Today the CVP delivers enough water to supply about one-third of the irrigated farmland in the state and close to a million households in the Central Valley and parts of the Bay Area.
The Colorado River Aqueduct (CRA) diverts a share of the water coming into California from the Colorado River. A 1922 agreement among the seven states that form the river’s drainage area paved the way for the construction of the Hoover Dam in 1936. Shortly after, construction began on a number of downstream storage and diversion structures, including the CRA, which was engineered, built and managed by the Metropolitan Water District of Southern California, a water-wholesaling agency that serves 26 member agencies in six counties from Ventura to San Diego. The CRA serves the water needs of Los Angeles and many other Southern California communities through a system of nine reservoirs, five pumping plants, 63 miles of canals, 92 miles of tunnels, and 84 miles of buried pipeline. Under the terms of compacts and treaties forged among seven Western states, several sovereign Native American tribes and Mexico, California is entitled to 4.4 million acre-feet of the Colorado’s water in normal years, though supplies have tightened in recent years as other states have begun to take their full allotment. In addition to the CRA, another major network called the All-American Canal System serves several irrigation districts in the Imperial Valley and elsewhere in southeastern California.
The State Water Project (SWP) was designed to deliver public water supplies from areas in the north, where water is plentiful, to areas of need in the Bay Area, Central Valley and Southern California. Citizens voted to approve the water system in 1960 and construction began in 1961 on SWP facilities including the Oroville Dam that spans the Feather River. By the mid 1960s, the first water deliveries were reaching the San Francisco Bay Area and what would later become Silicon Valley. In 1972 the SWP reached its southern limits: two canals veer east and west on the far side of the Tehachapi Mountains near Bakersfield. The Coastal Branch Aqueduct, a 116-mile long offshoot to Santa Barbara and San Luis Obispo, opened in 1997. Today the SWP boasts 32 storage facilities, reservoirs and lakes, 17 pumping plants, three pumping-generating plants, five hydroelectric power plants and about 660 miles of open canals and pipelines. Along the way water is supplied via 29 public water agency contractors to 23 million Californians and 775,000 acres of irrigated farmland. About 70 percent of SWP water is delivered to urban users and 30 percent to agricultural users.
The pumps for both the State Water Project and the Central Valley Project are located in the southern portion of the Sacramento-San Joaquin Delta. California’s largest estuary, the Delta is where the rivers of the western Sierra converge before heading toward San Francisco Bay. While these projects are considered engineering marvels and have provided the foundation for California’s economic success, they were not built to meet all the demands being placed on them today. Nor were they built with the Delta’s current environmental issues in mind — problems caused by a variety of factors including water diversions, invasive species and the loss of habitat. Due to the Delta crisis, the SWP and CVP are being challenged to provide for people and the environment even though the system wasn’t built to do both. State, federal and local agencies are working to develop long-term solutions to achieve that goal.
Next time you pour that glass of water, take a shower, or do a laundry load, think about all the natural and manmade contributions that go into delivering this precious resource. What steps can you take to assure that it will always be there? How can you and your neighbors use water more wisely? Right now, learning how to conserve must become our daily business.