Deeper Winter/Spring Drawdowns of Lake Roosevelt May Be Coming

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Published: Wednesday, 24 January 2024 21:28

Deeper Winter/Spring Drawdowns of Lake Roosevelt May Be Coming

September 2024 should be circled on your calendar. If the United States and Canada do not reach an agreement on modernizing the Columbia River Treaty by that time, treaty flood risk management provisions change to “called upon.” Called upon means the United States will call on Canada to specify flood risk management space needs from Canada, which (following a consultation) Canada must then provide.   Most important, the United States would need to demonstrate the use of all related storage before requesting Canadian space.

Instead of “called upon,” the U.S. Army Corps of Engineers now uses the phrase “real time operations” or “real time flood risk management” to describe what will occur.  

Last fall, the U.S. Army Corps of Engineers and Bureau of Reclamation hosted public webinars to explain the potential effect of this change in practical terms. Although there is a lot of uncertainty, the webinar’s intention was to make the public aware of potential changes with the assurance that agencies will share additional information when more is known.

In opening remarks, Brigadier General Geoff Van Epps, Northwestern Division Commander, said the change to real time operations “may lead to deeper drafts in Grand Coulee [Lake Roosevelt] as well as reduction in some flexibility.”

Figure A shows the potentially dramatic change to Lake Roosevelt water elevations. The blue line at the top shows, historically, average lake elevations month to month. Depending on seasonal weather conditions and how Canada may choose to operate its reservoirs after September 2024, the yellow line shows how deeply Lake Roosevelt could be drawn down, representing a worst-case situation. The shaded area shows the potential range in these average elevations during winter and spring if Treaty negotiations result in some degree of pre-planned or other operational benefits from Canada.

Figure A

Source: U.S. Army Corps of Engineers: https://www.nwd.usace.army.mil/CRWM/Columbia-River-Treaty/

Figure B provides an easy way to understand the need for additional drawdowns of Lake Roosevelt. Under current treaty provisions, the green area represents the dedicated reservoir storage Canada provides annually for flood risk management. Representing 8.95-million-acre feet, it “is about double the amount of water in Lake Roosevelt behind Grand Coulee Dam,” said Reservoir Control Center Chief Julie Ammann with the Northwestern Division of the U.S. Army Corps of Engineers.

Figure B

Available Columbia River System Storage Capacity

Source: U.S. Army Corps of Engineers webinar, www.nwd.usace.army.mil/CRWM/Columbia-River-Treaty/.

In September 2024, the Canadian dedicated flood risk management provision in the treaty sunsets. And with it, lost flexibility in managing Lake Roosevelt drawdowns to meet downstream flood control needs. While Treaty negotiations with Canada continue, the current level of Canadian flood risk management should not be expected to continue.

Eric Rothwell, a Columbia River civil engineer with the Bureau of Reclamation Pacific Northwest Region, noted the following increased potential drawdown effects to Lake Roosevelt:

• Temporary, seasonal closure of boat ramps during times when minimum lake elevation requirements are not met. As boat ramps have varied lake elevation requirements, how many boat ramps would be closed and for how long would be dynamic.
• Loss of Gifford and/or Inchelium ferry service during periods when lake levels are below docking requirements. Loss of service would affect medical emergency response, school activities, and other time sensitive needs.
• Increases in shoreline erosion and beach exposure.
• Potential negative effects to resident fish include entrainment (juveniles being forced past Grand Coulee Dam because of increased water flows) and potential decreased spawning habitat availability.
• The timing of pumping water to Banks Lake may be affected, with greater water level fluctuations, and the cost of pumping may increase. Irrigation water delivery to the Columbia Basin Project is likely to be unaffected.

An additional potential negative impact of deeper drafts not mentioned by the Corps and Reclamation is increased transport of contaminated sediment from upstream to downstream portions of the reservoir. Deeper and more frequent drawdowns also have the potential to alter the thermal structure in the reservoir and impact the size and composition of the planktonic communities, thereby affecting the food web. These changes may affect the Environmental Protection Agency’s Upper Columbian Remedial Investigation and Feasibility Study, particularly the Baseline Ecological Risk Assessment that is currently underway.

On the positive side, not mentioned is that white sturgeon recovery efforts may benefit because higher flows may mitigate recruitment failure at the larval stage, the time from hatching to developing into juveniles.

To view the webinar in full, visit https://www.nwd.usace.army.mil/CRWM/Columbia-River-Treaty/.

Negotiations to modernize the Columbia River Treaty began in May 2018. Since then, 18 rounds of negotiation have occurred. The U.S. Department of State leads the American negotiating team, which includes representatives from the Bonneville Power Administration, the Corps Northwestern Division, the U.S. Department of the Interior, and the National Oceanic and Atmospheric Administration. The U.S. delegation also includes expert advisors from the Coeur d’Alene Tribe, the Confederated Tribes of the Colville Reservation, the Kootenai Tribe of Idaho, and the Confederated Tribes of the Umatilla Indian Reservation. Click here for the Department of State’s most recent status update on negotiations.

If negotiations do not bear fruit, the real time operational changes to Lake Roosevelt begin in September.