Hydroclimatic change and connections to aquatic ecosystem management in the Grand Canyon

Abstract: The Colorado River below Glen Canyon Dam is a highly modified and managed system, hydrologically and ecologically. Competing demands for water and conflicting management goals have made it difficult to define and implement ecologically beneficial management practices. Projected warmer temperatures and declining runoff of approximately 10% by mid- century will make the already imbalanced supply and demand for water more severe. This will generally translate to less water available to address ecosystem concerns. Furthermore, hydroclimatic change adds complications for scientifically understanding ecosystem processes in this highly altered system and subsequently managing for ecosystem integrity. While direct impacts to aquatic ecosystems are an important part of assessing and planning for the future, the highly managed nature of the system means that human impacts will continue to dominate ecosystem process and function. Management actions have the capacity to build or erode ecosystem resilience to future perturbations. Thus, how water supply and hydropower needs are met within a changing climate has serious implications for ecosystem management opportunities. Continuing to study ecosystem responses to management actions, refine ecosystem goals, place ecosystem objectives in context of larger basin-wide objectives, and build the institutional flexibility to take different management actions will become even more important in the future.