The U.S. Environmental Protection Agency and the U.S. Geological Survey have released a fact sheet — Final EPA-USGS Technical Report: Protecting Aquatic Life from Effects of Hydrologic Alteration.
Hydrologic alteration is a change to an aquatic system and can include an increase or decrease in water volume, seasonal pulse flow disruption, dramatic variation in water temperature, and other factors.
Sources of flow alteration cited in the report are:
- Dams and impoundments (including for hydropower)
- Diversions (including for hydropower)
- Groundwater withdrawals
- Effluents and other artificial inputs
- Land-cover alteration
Stresses on aquatic life associated with hydrologic alteration may be further intensified through climate change, which may change the frequency and duration of extreme weather events, EPA says.
The report presents a literature review of the natural flow system and a description of the potential effects of flow alteration on aquatic life; examples of narrative water quality criteria some states have developed to support natural flow and maintain healthy aquatic biota; and a flexible framework that can be used by states, tribes and territories to quantify targets for flow regime components that are protective of aquatic life.
“Sound and sustainable management of aquatic ecosystems is an integral part of managing water resources to meet the needs of society and the goals of the Clean Water Act,” EPA says.
The complete report is available here.