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Abstract
Humans rely on freshwater ecosystems for a range of values including biodiversity, cultural, supporting, provisioning, and regulating services. Freshwater ecosystems have experienced significant changes to flow and nutrient regimes from human modifications. In addition, climate change has resulted in an increase in the frequency and severity of extreme weather events, like drought, resulting in reduced water availability for human and river ecosystem needs. It is critical to manage river ecosystems for both short-term human needs and long-term ecosystem services. In this dissertation, I examined how to manage for environmental outcomes when direct relationships between river flows and ecological outcomes are context dependent and policies and planning were built around municipal, industrial, and agricultural water needs. First, I examined environmental flow relationships for a submerged macrophyte, Podostemum ceratophyllum. I found an indirect effect of low river flows on Podostemum growth, mediated by algal and sediment accrual and grazing herbivores when water velocities were reduced. Next, I developed and integrated ecological indicators into Georgia’s State-wide Water Planning Framework. A few key themes emerged for developing the framework and ecological metrics for planning and for using the approach in other settings. Context dependency was important both for water resource decision-making and in selecting and evaluating environmental-flow outcomes for local systems. In addition, it was important to evaluate river ecosystem needs alongside other water uses and to provide the information to evaluate and interpret findings to planners or decision makers. In the final study, I evaluated management actions that could improve drought resilience in the Flint River in Georgia, U.S.A. I explored how increasing infiltration throughout the basin, augmenting flow with additional storage, and changing low-flow management operations could impact river flows. I found that management operations were the most critical factor for maintaining adequate river flows during drought periods, and if combined with additional storage would allow municipal utilities to meet short-term human needs without compromising long-term ecosystem services.