Designing and transferring environmental flows
MetadataShow full item record
Societal and environmental water needs are increasingly in conflict due to rising water demands from growing global human populations and climate-change-induced intensification of hydrologic drought. The last couple of decades have seen a blossoming of research in environmental flows – the provisioning of water within rivers to sustain freshwater ecosystems while maintaining societal water needs – to resolve these water conflicts. The unfortunate reality, however, is that societal water needs are outpacing our ability to utilize prevailing methodology for prescribing in-stream flows based on natural flow restoration and develop rigorous environmental flow recommendations on an individual river basis. My thesis addresses these challenges by first presenting in Chapter 1 a framework for designing environmental flows to balance the conflicting goals of meeting human water needs and benefiting native fish species over nonnative fish species, using novel holistic methods to quantify species’ flow-ecology relationships and multi-objective optimization to determine efficient flow recommendations for the San Juan River, NM. Flow designs were predicted to lead to greater gains in native fishes and losses in nonnative fishes as compared to natural flow mimicry. Moreover, flow designs minimized or circumvented conflicts between human and environmental water needs, even during periods of hydrological drought. The scope of these designs illustrated an encouraging future for ecosystem sustainability in regulated rivers. In Chapter 2, I address the gap between the desire to prescribe regional-scale environmental flows and the dearth of research that quantifies the transferability of flow-ecology knowledge meant to support environmental flow recommendations. Building on the flow-ecology modeling framework developed in Chapter 1, I elucidate the relationships of freshwater fish species with streamflow across five river basins in southwestern United States to quantify the transferability of flow-ecology relationships across space, time, and taxonomy. Species’ flow-ecology relationships transferred similarly well across different river basins as compared to within a river basin, though species in regulated rivers saw less transferability than those in free-flowing rivers. Species’ flow-ecology relationships transferred through time just as well as across space. Finally, fluvial dependence and life-history trait guilds proved to be strong conduits for transferring flow-ecology knowledge across taxonomy. Together, these chapters present crucial insights into and encouraging opportunities for the use of environmental flows to meet the goals of sustainable water use and freshwater species conservation in contemporary rivers around the globe.