IF YOU DRAW it on a map, the Colorado River has the shape of a tree, with its trunk rooted in the Sea of Cortez and the branches reaching into the mountaintops of Wyoming, Utah, Colorado, New Mexico, and Arizona. Botanists call the shape of a tree a habit. It is a common form in nature, like an artery branching to capillaries or nerves reaching to fingertips. But there’s always another part that isn’t shown, a looping back to start over. The water runs down the mountains to the ocean that pumps it back to the mountains by way of clouds. The shape is really a circle. The cloud part is just hard to draw on a map.
If I’m being honest, the cloud part is a pretty weak effort, because the Colorado River begins and ends in a desert, a place of little precipitation. The clouds come laden from the Pacific Ocean but expend much of their water as they cross the Sierras and Cascades. By the time they get to the Colorado Plateau and the Rockies they have little water left to give. The Colorado River Basin is a watershed that covers a big area, roughly the size of Texas. The Columbia River watershed is about as large but carries 12 times as much water. The Mississippi watershed is five times larger than the Colorado’s but carries 26 times as much water.
So we should admit and accept, up front, that the Colorado never was and never will be a mighty river system, and that it is climate-challenged and prone to drought. We never should have asked it for so much. We invaded it like cancer, turning water into property. I wish it wasn’t so.
Most of the water in the river system—some 90 percent—falls as rain and snow in the mountains of the Upper Basin. To go back to the shape of a tree, the Lower Basin of the Colorado is the trunk, and the Upper Basin is the branches. Snowmelt from the upper branches in rural Colorado, Wyoming, and Utah runs downstream to supply the Lower Basin and the cities of Los Angeles, San Diego, Phoenix, and Las Vegas. Because the river—the whole watershed or whole tree—is so prone to drought, we built the country’s two largest reservoirs, Lake Mead and Lake Powell, near the top of the trunk, below the branches, to ensure the West’s cities and farms don’t run out of water.
The last time these two reservoirs were at full capacity was in the summer of 2000. In 2022, after 22 years of drought, both reservoirs were at about one-quarter of capacity. If that rate of decline were to continue, they’d both be empty in six years. The deluges of last winter bought us some time. But they don’t change the fact that the Colorado River system is in dire straits. If the waterline drops below the dams’ intake ports, their electromagnetic dynamos, which can generate up to 3.4 gigawatts, will no longer be able to bring energy to 1.6 million people. After that comes the level called “dead pool,” where the water drops below the reservoirs’ outlet ports and can no longer flow through to the river’s lower stretches.
Dead pool on Mead and Powell could mean people in Los Angeles, San Diego, Phoenix, and Las Vegas would not be able to wash their dishes or flush their toilets or get a drink of water from their hoses. These city-states could collapse. This is why people are freaking out about the Colorado going dry.
The problem at hand is clear: Somehow we need to find water to refill the reservoirs. We can’t control the amount of precipitation that falls within the Colorado River watershed, but we can control how we use the water that’s available. If we use less, there will be more
