Besides providing irrigation water, the dams turn the power of falling water into electricity that lights homes for hundreds of miles around. Some dams do another important job for people who live in the Snake's wide valley. They control floods by storing water and releasing it slowly. In the spring, the Snake can be so full of water that it's fast and very dangerous. Because of that, early explorers called it the Mad River.
Dams also make lakes where thousands of migrating birds stop for a rest on their long flights.
But there is a problem with dams - and some people want to take out the four on the lower Snake River to make life easier for fish. Despite all the good dams do, they make it difficult for salmon to swim from streams where they are born to the ocean and back. Salmon are a very important part of the Northwest, and a species that many other animals depend on for food. Many devices are being used to make the trip for fish easier, but some salmon species are dwindling toward extinction anyway. One way the government tries to help the baby fish is by catching thousands of them and putting them into boats that float down the Snake and Columbia rivers past the dams.