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Open-File Report 2015–1027

Prepared in cooperation with the U.S. Army Corps of Engineers

Improved Algorithms in the CE–QUAL–W2 Water-Quality Model for Blending Dam Releases to Meet Downstream Water-Temperature Targets

By Stewart A. Rounds and Norman L. Buccola


Water-quality models allow water resource professionals to examine conditions under an almost unlimited variety of potential future scenarios. The two-dimensional (longitudinal, vertical) water-quality model CE-QUAL-W2, version 3.7, was enhanced and augmented with new features to help dam operators and managers explore and optimize potential solutions for temperature management downstream of thermally stratified reservoirs. Such temperature management often is accomplished by blending releases from multiple dam outlets that access water of different temperatures at different depths. The modified blending algorithm in version 3.7 of CE-QUAL-W2 allows the user to specify a time-series of target release temperatures, designate from 2 to 10 floating or fixed-elevation outlets for blending, impose minimum and maximum head and flow constraints for any blended outlet, and set priority designations for each outlet that allow the model to choose which outlets to use and how to balance releases among them. The modified model was tested with a variety of examples and against a previously calibrated model of Detroit Lake on the North Santiam River in northwestern Oregon, and the results compared well. These updates to the blending algorithms will allow more complicated dam-operation scenarios to be evaluated somewhat automatically with the model, with decreased need for multiple model runs or preprocessing of model inputs to fully characterize the operational constraints.

First posted February 6, 2015

Supplementary Material

For additional information, contact:
Director, Oregon Water Science Center
U.S. Geological Survey
2130 SW 5th Avenue
Portland, Oregon 97201

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Suggested citation:

Rounds, S.A., and Buccola, N.L., 2015, Improved algorithms in the CE–QUAL–W2 water-quality model for blending dam releases to meet downstream water-temperature targets: U.S. Geological Survey Open-File Report 2015-1027, 36 p.,

ISSN 2331-1258 (online)




Purpose and Scope

Blending Algorithms in CE–QUAL–W2

Modified Blending Algorithms for Version 3.7

Examples to Illustrate New Capabilities

Comparison Test of New Algorithms

Summary and Conclusions


Supplementary Material

References Cited

Appendix 1. Example w2_selective.npt Files

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