Sharing the Colorado River: How Seven States Divide One Basin

The Colorado River is one of the most fought-over rivers in the world. It begins high in the Rocky Mountains and flows more than a thousand miles toward the Gulf of California in Mexico. Its basin, including tributaries such as the Green and San Juan rivers, reaches into seven states: Colorado, Wyoming, Utah, New Mexico, Nevada, Arizona, and California. It also crosses the border into Mexico. Roughly forty million people depend on its water, and so do millions of acres of farmland. The river is not large enough to satisfy every claim on it. How its water is shared is decided not by nature but by law and negotiation.

The basic rules were set more than a century ago. In 1922, the seven states signed the Colorado River Compact. The compact drew a line across the basin and split it into two halves. The states above the line form the Upper Basin. The states below it form the Lower Basin. Each half was given a share of the river's water to divide among its own states. A later treaty, signed in 1944, promised a share to Mexico as well. Together these agreements are often called the Law of the River.

The compact rested on a hopeful guess. The people who wrote it measured the river during unusually wet years. They assumed more water flowed through it each year than usually does. Every share they handed out was based on that high estimate. For decades, the gap did not matter much, because not every state used its full share. As the region's cities grew and its farms expanded, demand caught up with the paper promises, and then passed them.

Farming takes the largest share of the water. Worldwide, agriculture accounts for roughly 70 percent of freshwater withdrawals, and the Colorado Basin follows that pattern. Fields of hay, vegetables, and winter lettuce in the desert depend on river water carried through long canals. Cities depend on it too. Las Vegas, Phoenix, and parts of Southern California all drink from the Colorado. Hoover Dam, which holds back the river to form Lake Mead, also runs a power plant with a rated capacity of about 2,080 megawatts, although years of drought and low water in Lake Mead have cut its power generation by about 30 percent.

In recent years, the shared system has been pushed to its limits. A long drought, made worse by a warming climate, has shrunk the river's flow. The two largest reservoirs, Lake Mead and Lake Powell, have fallen to their lowest levels since they were filled. When the reservoirs drop, there is less water to divide, and the old shares no longer add up. The states have been forced back to the table again and again to agree on cuts.

These negotiations show how hard it is to govern a shared resource across borders. No single state can solve the problem alone, because the river ignores state lines. The federal government helps set the terms and can step in if the states cannot agree, but it prefers that they reach their own deal. Mexico must be included through treaty. Native American tribes hold some of the oldest and strongest water rights of all, and they too have a seat at the table. Each round of talks tests whether many governments, with different needs, can share a river that is giving them less than it once did.

The Colorado shows a pattern that appears wherever water crosses a border. The physical river shapes the politics, and the politics decide who gets the water. When the river changes, the agreements must change with it.

1. How many states share the Colorado River, and what are the two basins the compact created?
2. In what year was the Colorado River Compact signed, and what did it do?
3. What mistake did the authors of the compact make when they estimated the river's flow?
4. Explain why the "paper promises" did not cause problems at first but do now.
5. Why does the passage say that no single state can solve the shortage on its own?
6. Besides the seven states, who else holds a claim to the river's water? Name two, according to the passage.
7. The passage ends by saying the physical river shapes the politics and the politics decide who gets the water. Explain what this means using one example from the text.