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Title:Optimization Techniques for Instream Flow Allocations
Author(s):Sale, Michael John
Department / Program:Civil Engineering
Discipline:Environmental Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Environmental Sciences
Abstract:The issue of instream flow maintenance is an aspect of environmental quality which is now required as part of the project planning process of water resources development. A mathematical programming methodology is developed which provides an analysis technique for multipurpose reservoirs for both biological instream flow needs (IFN) and more traditional water project objectives such as water yield, flood control or economic efficiency. The constrained optimization approach used combines an implicitly stochastic modeling technique for surface reservoirs known as the linear decision rule (LDR) with an objective function representing the instream value of reservoir releases to downstream fisheries. Operating policies for a reservoir are defined in a set of LDR chance constraints which enforce the satisfaction, at specified reliabilities, of water use goals other than those required to meet biological IFN. Values for instream flows which are maximized are based on the median committed releases produced from the LDR operating policy.
The attribute used to quantify instream flow values is an index of physical habitat condition termed weighted usable area (WUA) derived from modeling techniques developed by the U. S. Fish and Wildlife Service. WUA is a measure of the overall suitability of physical habitat (two dimensional variation of velocity, depth and bottom substrate) for various target fish species and life stages of each species. The habitat response functions (WUA vs. stream discharge) are formulated into a maximum objective function which sets instream flow values equal to the minimum habitat condition over all life stages of a target species and all time periods in a planning cycle. The reservoir optimization program which is created has both linear and nonlinear inequality constraints and can be solved efficiently by using a Generalized Reduced Gradient algorithm. The structure of the maximin objective also lends itself to a piecewise linear approximation to which linear programming solution algorithms can be applied.
A case study of Lake Shelbyville, a multipurpose reservoir in central Illinois, is presented to demonstrate the application of the optimization methodology for coupling existing requirements of flood control and reservoir-based recreation with IFN. The WUA decision criterion does not include all the important considerations such as water quality or nutrient and energy fluxes which are required to ensure "biological integrity" of regulated stream ecosystems. However, it is shown that the approach can provide significant insights into reservoir management policy for IFN, especially in the development of a long-term operating strategies (i.e, rule curves). Extensions of the general modeling approach include addressing IFN in the context of multiple reservoir systems, hydroelectric power development and ultimately more comprehensive biological attributes which can more fully represent the dynamics of aquatic ecosystems.
Issue Date:1981
Description:175 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1981.
Other Identifier(s):(UMI)AAI8114473
Date Available in IDEALS:2014-12-13
Date Deposited:1981

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