Turning dreams into reality: Challenges to developing flow-ecological relationships to support regional streamflow management

The importance of hydrologic variability for shaping the biophysical attributes and functioning of riverine ecosystems is well recognized.  In addition to the ecological dependences of flow for aquatic organisms, human societies modify natural flow regimes to provide dependable ecological services and to seek protection from floods.  Understanding patterns of hydrologic variation and quantifying the associated ecological responses of altering these patterns, has therefore become fundamental to water management planning.  Here, we introduce a new research initiative to advance streamflow management in Washington State.  Our approach follows the Ecological Limits of Hydrologic Alteration (ELOHA) framework by synthesizing data collected from individual rivers into a scientific framework that supports the development of environmental flow standards at the regional scale.  A key element of ELOHA is the development of relationships between flow alteration and ecological characteristics for different river types based on paired streamflow and ecological data from throughout the region of interest.  At first glance this task may seem relatively straightforward.  However, in reality the ability to develop flow-ecological relationships that are statistical robust, ecologically meaningful, geographically transferable, and relevant to water management and policy, is much more complicated.  We discuss these key challenges by reflecting on our efforts in Washington State.