Hydropower is better for the environment than other major sources of electrical power, which use fossil fuels. Hydropower plants do not emit the waste heat and gases—common with fossil-fuel driven facilities—which are major contributors to air pollution, global warming and acid rain. The mining and drilling required to acquire fossil fuels for other power sources also have a significant negative environmental impact.

Many hydropower plants are located in the headwaters of river basins where they can help control the wide fluctuations in water flow commonly found in these areas. By increasing water flow during dry months these projects help to enhance aquatic habitats. Conversely, by reducing flow during periods of heavy runoff the plants can prevent damage to vegetation and wildlife along stream banks.

However, hydropower projects and the dams associated with them do change the natural river environment, and there is often a price to pay for these changes. USACE works closely with natural resources agencies to minimize the negative environmental impact of all of its hydropower projects.

For instance, in the southeastern states, dissolved oxygen levels below dams often get so low that aquatic life is severely affected. USACE is working to improve dissolved oxygen levels at these facilities by using aerating turbines and injecting oxygen directly into the streamflow.

Over time the public has come to realize that we need a balance between improving our immediate daily environment and in preserving the natural environment around us. The USACE response is a concerted effort to mitigate dam and reservoir impacts to make the operation of these projects more compatible with the environment. USACE is constantly striving to strike the appropriate balance between the nation's need for a clean, inexpensive, efficient power source and environmental concerns.