The Range of Variability Approach
A good way to address this key watershed management question is through the "Range of Variability Approach" (RVA), which is based upon two overarching principles:
River ecosystems and the native species dependent upon them can best be conserved by protecting as much as possible of the natural variability in flow, a concept that has been called the "natural flow paradigm."
Because we will not perfectly understand how much alteration of natural flow regimes is ecologically tolerable in any particular river, the definition of an adequate or preferred flow regime should be determined in an adaptive fashion, a concept that has been called "adaptive management."
The Adaptive Management Cycle goes from Site Conservation Plans to Baseline Monitoring to
Strategy Implementation to Measuring Progress and back to Site Conservation Plans.