Decision Trees for Incorporating Hypothesis Tests of Hydrologic Alteration into Hydropower–Ecosystem Tradeoffs
Publication: Journal of Water Resources Planning and Management
Volume 146, Issue 5
Abstract
Short streamflow records make it difficult to determine the extent to which discharge changes in excess of ecological thresholds are due to dam operations or natural variability. Unnecessary changes to reservoir operating rules can reduce off-stream benefits, whereas no changes to rules when thresholds are exceeded can degrade downstream riverine ecosystems. We introduce a Bayesian decision tree approach to a hypothetical hydropower–ecosystem decision problem that compares expected in-stream and off-stream losses resulting from incorrect decisions. Expected losses are computed using loss probabilities derived using Bayes’ theorem, type I and II errors, and prior probabilities of alteration. Decision-tree recommendations compared with those from deterministic and null hypothesis significance testing under a variety of conditions illuminate the benefits of including valuations of hydropower and ecological losses as well as type II error probabilities in reservoir operation decisions. This is the first study to both introduce and demonstrate the value of Bayesian decision trees for addressing tradeoffs between hydropower and ecosystem benefits and losses.
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Data Availability Statement
The streamflow data used in our hypothetical case study, along with code for the reservoir simulation model, Mann-Whitney test (including power analysis), and Bayesian decision tree, are available in a Github repository at https://github.com/jshecht/EnvFlows_DecisionTree. Additional code produced during the study is available from the corresponding author by request.
Acknowledgments
This work builds on a conference paper (see Hecht et al. 2015) and dissertation (Hecht 2017). The Hydro Research Foundation provided a research award to the first author through a grant from the United States Department of Energy (DOE). The National Science Foundation’s Integrative Graduate Education and Research Traineeship (IGERT) program in water diplomacy at Tufts University (NSF OIA #0966093) and Vermont Experimental Program to Stimulate Competitive Research (EPSCoR) program (NSF OIA #1556770) also provided in-kind support. Ryan McManamay was supported by the US DOE, Office of Energy Efficiency and Renewable Energy, Water Power Technologies Office. This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the US Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).
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Journal of Water Resources Planning and Management
Volume 146 • Issue 5 • May 2020
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©2020 American Society of Civil Engineers.
History
Received: Oct 10, 2018
Accepted: Sep 24, 2019
Published online: Feb 18, 2020
Published in print: May 1, 2020
Discussion open until: Jul 18, 2020
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