Large-scale Flow Experiments for Managing River Systems

Abstract

Experimental manipulations of streamflow have been used globally in recent decades to mitigate the impacts of dam operations on river systems. Rivers are challenging subjects for experimentation, because they are open systems that cannot be isolated from their social context. We identify principles to address the challenges of conducting effective large-scale flow experiments. Flow experiments have both scientific and social value when they help to resolve specific questions about the ecological action of flow with a clear nexus to water policies and decisions. Water managers must integrate new information into operating policies for large-scale experiments to be effective. Modeling and monitoring can be integrated with experiments to analyze long-term ecological responses. Experimental design should include spatially extensive observations and well-defined, repeated treatments. Large-scale flow manipulations are only a part of dam operations that affect river systems. Scientists can ensure that experimental manipulations continue to be a valuable approach for the scientifically based management of river systems.biological conditions in these systems may not be attributed solely to the level of streamflow during the experiment. Unlike experiments on land, lakes, and small streams in experimental watersheds, flow manipulations involving whole rivers or estuaries can rarely, if ever, be isolated from their social context. Stakeholders have diverse interests in how water is used, and water managers operate facilities and systems to achieve multiple objectives. The overarching issue for scientists involved in large-scale flow experiments, then, is to design scientifically credible and tractable investigations that simultaneously inform water management about policies to achieve long-term objectives.We review the global practice of flow manipulations in rivers as large-scale experiments to guide future efforts in this burgeoning area of interest using examples from over 40 systems (see the supplementary material, available online at http: //dx.doi.org/10.1525/bio.2011.61.12.5). We focus on flow manipulations intended to achieve ecological objectives because of their direct relevance for informing dam operations but recognize that investigations of natural flow events and manipulations not intended for ecological outcomes provide useful information for managing rivers and advancing river ecology. We identify how flow experiments have elucidated and addressed facets of the complexity in river, floodplain, and estuary ecosystems. These examples lead us to a core set of challenges and principles for conducting effective large-scale flow experiments that have both scientific and social value.

A Tale of Two Rivers: Implications of Water Management Practices for Mussel Biodiversity Outcomes During Droughts

“…Although minimum flows have been discussed for decades (Gore 1978), large-scale natural or manipulative flow experiments generally manipulate flood occurrence and/or frequency rather than increasing minimum flows (Konrad et al 2011). Increasing minimum flows has been shown to increase the ecological integrity of benthic aquatic insect and fish communities (Connor and Pflug 2004;Bednarek and Hart 2005;Decker et al 2008;Bradford et al 2011), but these studies often restore flows with the purpose of rewetting previously dry reaches instead of increasing existing flows (but see Travnichek et al 1995).…”

Research Priorities to Improve Future Environmental Water Outcomes

“…River ecosystems are influenced by a wide range of factors, including species interactions, temperature, and sediment dynamics, that may interact in numerous unspecified ways with flow alteration (Acreman et al, 2014). With much research still reliant on drawing patterns from uncontrolled changes in flow conditions during floods or droughts, a major challenge is to undertake controlled water management experiments at the catchment scale (Konrad et al, 2011;Olden et al, 2014). More collaboration between dam owners/operators, landholders, and scientists is needed to codevelop hypotheses and provide robust tests of these via flow manipulation experiments (Poff et al, 2003).…”

“…The challenge and urgency of protecting water regimes is global, but significant advances in environmental water science, policy, and practice have been unevenly distributed among countries and biophysical, social, cultural, and political settings (McClain and Anderson, 2015). A present-day cartogram of published research efforts on environmental flows would be heavily skewed toward North America, Europe, and Australia (Poff and Zimmerman, 2010;Konrad et al, 2011).…”

Riverine Ecosystem Management

“…This highlights the importance of sustaining the learning process long enough to achieve such clarification. This deeper level of learning, e.g., doubleloop learning, involves probing the decision-making process itself and how social and institutional relations and stakeholder perspectives influence it (Torbert et al 2004;Argyris 1976Argyris , 2005Argyris and Schön 1978;Williams 2011). Double-loop learning can enable shifts in underlying beliefs, values, and mental models.…”