Hoover Dam - Environmental Impact

Environmental Impact

The changes in water use caused by Hoover Dam's construction has had a large impact on the Colorado River Delta. The construction of the dam has been credited as causing the decline of this estuarine ecosystem. For six years, after the construction of the dam and while Lake Mead filled, virtually no water reached the mouth of the river. The delta's estuary, which once had a freshwater-saltwater mixing zone stretching 40 miles (64 km) south of the river's mouth, was turned into an inverse estuary where the level of salinity was higher close to the river's mouth.

The Colorado River had experienced natural flooding before the construction of the Hoover Dam. The dam eliminated the natural flooding, which imperiled many species adapted to the flooding, including both plants and animals. The construction of the dam devastated the populations of native fish in the river downstream from the dam. Four species of fish native to the Colorado River, the Bonytail chub, Colorado pikeminnow, Humpback chub, and Razorback sucker, are currently listed as endangered.