Environmental flows – evolving the science to advance freshwater sustainability in a complex present and an uncertain future

Maintaining dynamic environmental flows to support aquatic ecosystems has emerged as a leading concern in the sustainable management of fresh waters throughout the world. Managing for flow variability stands in stark contrast to earlier formulations for minimum environmental flows (e.g., 7Q10), and the scientific challenges in specifying flow needs for ecosystems are non-trivial. New approaches (such as ELOHA) call for establishment of flow alteration-ecological response curves tailored to different types of natural flow regimes that can be empirically tested and refined at different levels of quantitative resolution and according to variable societal preferences. One key scientific hurdle in moving forward is a better understanding how flow interacts with other environmental drivers of ecosystem structure and function. Another is striking a balance that allows scientific defense of methods and inferences on the one hand and relevance to management and on the other. Scientists are increasingly collaborating with managers and stakeholders to develop ecologically effective and politically viable environmental flow policies. As human population growth and climate change exacerbate stress on aquatic ecosystems, environmental flows science needs to expand beyond its current at-a-site management focus to consider principles of regional-scale ecological resilience that can guide water infrastructure planning and development.