Do “Designer Flows” for Native Fish Also Protect Aquatic Insects and Riparian Plants?

Authors: David Lytle, Jonathan Tonkin, Julian Olden, David Merritt, Lindsay Reynolds, Jane Rogosch

Year: 2018

Abstract

Designer flow optimization for dammed rivers is a powerful approach for balancing ecological objectives and competing societal demands for water. How designer flows, which use flow events to target select species of interest, affect non-target ecosystem components has been largely overlooked. Using empirically-parameterized population models based on the Verde River, Arizona ecosystem, we found tradeoffs associated with designer flow regimes targeting riparian vegetation, fishes, and invertebrates. The different event frequencies associated with each designer flow regime resulted in some nontarget ecosystem components becoming functionally extinct in as little as 50 years. By incorporating multiple flow frequencies, the natural flow regime enabled a balanced response of the three components. Although returning to a natural flow regime may no longer be viable in highly managed rivers, designing river flows to support entire ecosystems must begin from natural flow regime principles.