On a map, the watersheds of the American West are distinct geographical features, framed by imposing plateaus and towering mountain ridges.
A closer look shows those natural boundaries are less distinct. A sprawling network of pipelines and canals pierce mountains and cross deserts, linking many of the mighty rivers and smaller streams of the West. These “mega-watersheds” have redrawn the map, helping cities and farms to grow large and productive. But they have also becoming political flashpoints with steep environmental costs.
Bill Hasencamp is with the Metropolitan Water District of Southern California, a wholesale water provider known as Met. He sees the western watersheds as a single interconnected system. Hasencamp speaks from the perspective of Southern California, a region that draws water from basins hundreds of miles away in Northern California and from the Colorado River. Hasencamp manages Colorado River resources, so he has one eye on Met’s 19-million person home territory while the other peers across the Mojave Desert at another supply – the shrinking lakes Mead and Powell.
Not every river in the West is linked and few regions are as networked as Southern California. But there are enough connections to assure that the water supply effects in the drying American West are not isolated. They involve neighboring watersheds.
Here’s an example, starting in Northern California: the Trinity River Diversion, a federal project, connects the Klamath River basin to the Sacramento River watershed. The Sacramento River flows south until meeting the San Joaquin River in the West Coast’s largest estuary. Water from the two rivers is pumped, via state and federal canals, to counties south of the Sacramento-San Joaquin Delta.
Once the Northern California water arrives in Southern California, it mingles with water from the Colorado River. That water is imported through the Colorado River Aqueduct, nearly 250 miles long. Upstream on the Colorado River, there are more links. Tributary streams in Colorado are diverted through the San Juan-Chama [cha as in charm] Project into New Mexico, where the water enters the Rio Grande system and supplies Albuquerque and Santa Fe. The Central Utah Project pulls Colorado River water into the orbit of the fast-growing Wasatch Front, which is outside the basin.
In the headwaters state of Colorado, 11 major interbasin transfers unite rivers on both sides of the Rockies. The Moffat and Adams tunnels cut through the Continental Divide, a feat of engineering that brings Colorado River water into the South Platte River basin, where it is gulped by Denver and other Front Range cities.
Smaller projects also crisscross the landscape. San Francisco reaches into the Tuolumne River. Los Angeles taps the Owens River. The Potter Valley Project diverts water from Northern California’s Eel River into the Russian River, which flows through Sonoma wine country.
Water managers like Hasencamp appreciate having a range of sources to draw from. If one area is dry, they can turn to another watershed. Hasencamp said “It’s just one egg in a big basket.” Problems develop when several of those eggs turn out to be rotten at the same time. The weather in northern California affects water supplies not only in Southern California, but also in cities, farms, and ecosystems throughout the Colorado River’s mega-watershed. When Northern California is dry, Hasencamp’s agency pulls more water from the Colorado River. That puts added pressure on Lake Mead, which is at its lowest point since it was filled in the 1930s.
These diversions offer flexibility, but they have consequences – both environmental and social. For example, they have depleted water for native fish. And many of these diversions — from the Owens River in California to the West Slope of Colorado — flow with a legacy of acrimony and mistrust, stirred up decades ago by the political imbalance between the rural areas where water was extracted and the urban areas where that water got sent.