Informing flow management decisions in the Middle Oconee River

Abstract

Whether justified by economic, environmental, or socio-cultural ends, there is a strong imperative for thoughtful management of freshwater resources. Meeting this need requires a framework for river management decisions that is transparent, fair, repeatable, and capable of explicitly stating trade-offs. Although the importance of “environmental” or “instream” flows is widely acknowledged, challenges arise in specifically identifying what flow regime is needed to obtain a desired ecological state. Taken as a whole, this dissertation sought to inform environmental flow decision making in the Middle Oconee River near Athens, Georgia.

Operated by a four-county authority, Bear Creek Reservoir is an off-channel, pump-storage reservoir, which withdraws water from the Middle Oconee River for municipal water supply. This dissertation applied a structured decision making framework to examine some of the economic and ecological trade-offs associated with alternative pumping schemes. In particular, the collective body of this dissertation addressed a single question: How can the water authority withdraw water from the Middle Oconee River with the least ecological impact?

Rather than recommending a flow regime, my goal was to inform decision-makers of the advantages and disadvantages of alternative withdrawal schemes. To do so, I developed a variety of techniques which incorporate novel dimensions not commonly addressed in environmental flow decisions (e.g., data visualization, hydrologic simulation, effectiveness analysis, value-laden decisions). As applied to the Middle Oconee River, these analyses indicate that current regulatory and management approaches are consistently outcompeted by novel environmental flow schemes relative to both withdrawal volumes and ecological endpoints of hydrologic similarity, fish recruitment, sediment transport, and organic matter transport. Although developed in the context of a single river, this dissertation provided a structured and rational approach which is broadly applicable to informing environmental flow decision making.