The natural, seasonal patterns of rising and falling water levels in freshwater systems shape aquatic and riparian habitats, provide cues for migration and spawning, distribute seeds and foster their growth, and enable rivers, lakes, wetlands, and estuaries to function properly. Altering the natural flow pattern – by damming, diverting or channeling water – takes a serious toll on the plants and animals that depend on it. If natural patterns and volumes of water flow are altered too greatly, freshwater ecosystems and species suffer.

Native species need natural flow patterns to flourish; too much flow alteration by humans has real impacts on biodiversity. But how much is too much?

The Nature Conservancy is a global leader in the science of environmental flows – determining the quantity and timing of water flows required to maintain the components, functions, processes and resilience of aquatic ecosystems and sustain the goods and services they provide to people. Determining environmental flows also determines the quantity and timing of flows that are available for humans to alter or divert safely, without harming aquatic ecosystems.

Working in partnership with government agencies, multilateral institutions, water management agencies, the hydropower industry, the scientific community and other non-governmental organizations around the world, Conservancy staff:

 Key Resources