THE CHALLENGE OF PROVIDING ENVIRONMENTAL FLOW RULES TO SUSTAIN RIVER ECOSYSTEMS

TLDR

Accounting for natural differences in flow variability among rivers is essential for protecting freshwater biodiversity and maintaining ecosystem services, yet many managers favor simplistic static flow rules that ignore this complexity. The authors contend that such simplistic rules are harmful and propose a generic, empirically validated approach that bridges simple rules and comprehensive assessments. They propose a class‑specific method that incorporates key aspects of natural flow variability and can be calibrated with empirical biological data.

Abstract

Accounting for natural differences in flow variability among rivers, and understanding the importance of this for the protection of freshwater biodiversity and maintenance of goods and services that rivers provide, is a great challenge for water managers and scientists. Nevertheless, despite considerable progress in understanding how flow variability sustains river ecosystems, there is a growing temptation to ignore natural system complexity in favor of simplistic, static, environmental flow "rules" to resolve pressing river management issues. We argue that such approaches are misguided and will ultimately contribute to further degradation of river ecosystems. In the absence of detailed empirical information of environmental flow requirements for rivers, we propose a generic approach that incorporates essential aspects of natural flow variability shared across particular classes of rivers that can be validated with empirical biological data and other information in a calibration process. We argue that this approach can bridge the gap between simple hydrological "rules of thumb" and more comprehensive environmental flow assessments and experimental flow restoration projects.