US Army Corps of Engineers
Northwestern Division

Columbia River

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Flood Risk & Forecast Information

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In January 1999 the Corps of Engineers released a report documenting the work to date on the development of a flood control operation for Libby Dam and Hungry Horse Dam called VARQ. The report was written in response to the Supplemental Biological Opinion on the Operation of the Federal Columbia River Power System dated, May 14, 1998, requesting a status report on the progress of the VARQ studies.

VARQ was developed to improve the multi-purpose operation of Libby and Hungry Horse while maintaining the current level of system flood control protection in the Columbia River. VARQ reduces the contribution of reservoir space at Libby and Hungry Horse for system flood control of spring runoff in the Columbia River in years with low to moderate potential for flooding. The procedure was designed to provide higher outflows from the projects during the spring runoff than under the current flood control operation as outlined in the Columbia River Treaty Flood Control Operating Plan. These outflows are more consistent with releases made to meet flow objectives for the listed Endangered Species Act Kootenai River white sturgeon and Columbia and Snake River salmon and steelhead.

The report is comprised of an Executive Summary and four sections, which are listed below.

Section 1. The Effects of VARQ at Libby and Hungry Horse on Columbia River System Flood Control, with appendices, Appendix A. VARQ Operating Procedures

Section 2. Kootenai River Flood Control Study, Analysis of Local Impacts of the Proposed VARQ Flood Control Plan

Section 3. Local Effects of the Proposed VARQ Flood Control Plan at Hungry Horse Dam, Montana

Section 4. The Effects of VARQ at Libby and Hungry Horse on Columbia River System Hydropower

Storage Reservation Diagrams define the flood control space required in each reservoir to provide flood protection for the Columbia River. Storage space required is a function of time of year and the seasonal runoff volume. The diagrams are designed to provide an orderly evacuation of each reservoir prior to the reservoir refill period with consideration to project operating limits and the regulation of the Columbia River reservoir system. The May 2003 Columbia River Treaty Flood Control Operating Plan contains a complete description of the flood control operation of the Columbia River.

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