Monday April 21, 2025
Water Education Foundation —
Before the construction of Hoover Dam on the lower Colorado River, as well as a slew of smaller sisters downstream, the stretch downriver served as a biological oasis in the middle of the unrelenting Mojave and Sonoran deserts. The marshes and backwaters along the river’s edge provided sheltered areas for fish to spawn and rear their young, and mesquite and cottonwood-willow forests provided important habitat for numerous species of birds and other animals. But when Lake Mead began filling behind Hoover Dam in 1935, it drastically reduced the amount of water flowing downstream, radically altering the habitat there.
In the decades that followed, the river flow captured by Hoover Dam became a critical source of water for farms and cities across Southern California, Nevada and Arizona – transforming deserts into some of the nation’s most productive farmland and creating some of the most populous cities such as Los Angeles, Phoenix and Las Vegas. Today, more than 27 million people in the three states rely on water from the Colorado River—roughly two-thirds of the total population that the river serves. Yet even as that dependence on the river grew, a collision between human and environmental needs was brewing.