The World Commission on Dams chronicled both the economic benefits of dams and the damage they have caused to water-dependent ecosystems and human production systems. With few exceptions, the world’s hydraulic infrastructure projects have been operated for a limited set of economic objectives and without consideration of the environmental consequences. Yet riverine ecosystems and the myriad species they support are shaped by, and dependent on, the timing, magnitude, duration, and frequency of flow patterns. Excessive changes in any one of these four variables can lead to the collapse of entire fisheries and ecosystems. The consequences for the downstream river basin can be profound.
By altering the natural flow regime, dams often:
- Diminish seasonal inflows of freshwater and nutrients into the ocean, disrupting the estuarine hydrodynamics that are the engine for the exceptional biological fertility at the freshwater/salt water interface; and
- Cause native fisheries to suffer while providing new habitat for exotic invaders.
In recent years, increasing attention has been paid to the ecological benefits of reoperating dams to store and release water in a pattern that more closely resembles natural flow conditions with their seasonal variability. The aiming point is to operate the reservoir more as a run-of-the-river facility and less as a storage facility. However, relatively little attention has been paid so far to techniques enabling these dams to make such environmental flow releases a permanent operational feature without reallocating water from economic to environmental uses. The Global Dam Reoptimization Initiative is focused on solutions intended to fill that information gap.
