Stochastics and ecohydrology: a study in optimal reservoir design

Abstract

The concept of environmental flow assessment is a crucial element of modified ecosystems featuring large infrastructure such as dams and reservoirs, but the relatively short length of available inputs raises questions about the reliability of any given environmental flow scheme. However, with the use of stochastics, it is possible to quantify these uncertainties, and present a solution that incorporates long-term persistence into a balanced reservoir simulation model. In this study, an attempt is made to determine a scheme that can produce a reliable timeseries of fluctuating environmental flows matching original river conditions to best accommodate local wildlife, in accordance with newer studies. The primary goal is to protect the ecosystem, and then secondarily to allow a steady supply of water for other uses. Using a synthetic timeseries based on historical inputs, it is possible to determine essential statistical flow characteristics, leading to a flow scheme that maximises environmental and human demand reliability. Undeniably, there seems to be a clear correlation between reliability and reservoir capacity, linking large sizes to cost-efficient design. However in an age characterised by an ever-changing climate and growing tensions between stakeholders, protecting the environment while also meeting design needs presents a daunting prospect for dam engineers.