Management of Water Supply Shortages to Sustain an Endangered Fish Species

Abstract

Arid and semi-arid landscapes globally represent significant challenges in developing and managing regional water resources for human uses while simultaneously sustaining aquatic ecosystems. Allocation of water resources between these divergent purposes requires careful analysis of the variable nature of the water supply and the plurality of demands on that supply if economic and ecological values of water are to be sustained. Where water resources are limiting, sustainability management of short-lived fish species may depend on adjusting the timing and quantity of out-of-channel diversions of water to reduce mortality-causing flow intermittence. Such management efforts can include strategies for improved water transport efficiency to increase the amount of water available for environmental flow. This work addresses gaps in the published literature by formulating and applying an analytic process that integrates demography of an endangered freshwater fish species, hydrology for a river segment with a high frequency of seasonal flow intermittence, and measures of cost-saving water management strategies to achieve environmental and economic objectives. This process provides a useful context for adaptive water resource planning that focuses on promising management actions needed to limit flow intermittence while serving to sustain socioecological systems. Much of the theory underpinning of management for ecological restoration and species sustainability is founded on an understanding of population ecology and the identification of factors that regulate population growth. We present an analytic process that integrates hydrologic and demographic factors in estimating the amount of water needed to supplement in-channel flow and so maintain surface water conditions that are minimally needed for short-term species survival. Demographic simulation results reveal distinct patterns in problem-solution sets that provide managers with much needed insight in planning effective and flexible responses to management challenges arising from unstable hydrologic conditions. Where water resources are limiting, sustainability management of short-lived freshwater fish species may depend on adjusting the timing and quantity of out-of-channel diversion of water to reduce mortality-causing flow intermittence. Investments in water transport efficiency increase the amount of water available for environmental flow while reducing potential conflicts with and between concerned and/or affected constituencies.