Canada will store several million-acre-feet of water that can be used in 2025 and for the next 20 years to help prevent floods in the Columbia River basin downstream in the United States, according to a virtual briefing earlier this month by federal dam operators on the Columbia River Treaty Agreement in Principle’s flood risk management protections.
However, that’s just about half the amount of pre-planned flood control storage provided over the past 60 years when the 1964 Columbia River Treaty agreement was in effect.
In 2025, Canadians will hold back some 3.6 MAF of preplanned space each year at the Hugh Keenleyside Dam (Arrow Dam) in British Columbia to aid flood risk management in the U.S. at Grand Coulee Dam and lower downstream in the Columbia River, mostly during spring runoff when water levels in the river rise. That’s a drop from the as much as 7.1 MAF of preplanned storage from Canada for flood risk management that was included in the previous Treaty agreement. In the earlier Treaty agreement, about 5.1 MAF was dedicated for flood control management with an additional 2 MAF of accessible storage when needed in real time.
The new arrangement for 2025 places more of the responsibility on the U.S. to manage its own flood risks and that will require changes to flood control protocols at Coulee and at the John Day Dam further downstream on the Columbia.
“The Canadian portion of the Columbia River in Canada may seem small, but it is responsible for much of the flooding lower in the river,” General William C. Hannon Jr. said at the virtual Treaty briefing, Dec. 4. Hannon is commander of the Corps’ Northwest Division office. “Nearly 40 percent of the floodwaters originate in Canada.”
In certain spring runoff conditions when flooding is threatened, the difference in storage between the 7.1 MAF of the previous Treaty and the preplanned 3.6 MAF of the new Treaty will have to be made up by drawing down both Lake Roosevelt, the reservoir backed up behind Grand Coulee Dam and the John Day Dam, effectively providing more of the storage needed to deter flooding in the U.S.
“Grand Coulee will likely experience deeper and longer duration drawdowns in some years,” said Steve Barton, chief of the U.S. Army Corps of Engineers’ Water Management Division. “Flows downstream will generally remain the same.” Grand Coulee is operated by the Bureau of Reclamation.
Barton said that Coulee is a huge storage dam and can be drafted 82 feet from a low 1,208 feet elevation above sea level to 1,290 feet of elevation. “Without the agreement, Coulee could have been drafted even lower,” he said.
In dry to average years, which is 60 percent of all years, the BOR would on average draft Coulee to a low of 1,270 feet prior to the new Treaty, but in 2025 Coulee could be drafted to as low as 1,260 feet.
With above average water, which is 30 percent of years, the Bureau could draft Coulee 7 feet deeper in 2025 at some point during March through May.
In very wet years, which is 10 percent of years, there would be very little change from the old Treaty to the new. That’s because Coulee will already be drafted to a low level to account for deep snowpacks.
The driest l0 percent of years and the wettest 10 percent should be similar, Barton said.
The Corps could also call on the John Day Dam and its reservoir for storage space. Although seldom used for storage or flood control, Barton said the dam and its reservoir is authorized for flood control use. The reservoir can be drawn down as much as 11 feet at some point between April and June.
“Before Sept. 2024, this operation was needed approximately 10 percent of the years,” he said. “Moving forward, we expect to see this in about 20 percent of years.”
Flood risk management is a provision of the Columbia River Treaty Agreement in Principle reached by the two countries July 11. The AIP that took effect in September is a roadmap for each country’s negotiation team to modernize the 60-year-old Columbia River Treaty, which has played an important role in guarding against and reducing flood damage in the U.S. and providing electricity to millions of households, businesses and industries in both countries. Originally ratified in 1964, the countries have agreed to continue the transboundary water management agreement, but with the addition of provisions that protect and support communities and ecosystems in both countries. The original Treaty expired this year in September.
The AIP took British Columbia and U.S. treaty negotiators some six years to negotiate. Canada and the U.S. are in the process of negotiating interim agreements that would be in effect during the period between when the AIP was reached and a modernized Treaty is brought into play.
See CBB, September 28, 2024, CANADA LOOKING FOR A NEW COLUMBIA RIVER TREATY TO PROMOTE ECOSYSTEM FUNCTIONS, CULTURAL VALUES OF B.C., FIRST NATIONS, HTTPS://COLUMBIABASINBULLETIN.ORG/CANADA-LOOKING-FOR-A-NEW-COLUMBIA-RIVER-TREATY-TO-PROMOTE-ECOSYSTEM-FUNCTIONS-CULTURAL-VALUES-OF-B-C-FIRST-NATIONS/
While the original Treaty was in effect, Canada had committed for 60 years to store water to reduce the risk of flood downstream in the U.S. Prior to the 1964 Treaty, which led to the construction of several storage dams in British Columbia and the John Day Dam in the lower Columbia River, flooding would typically occur up and down the Columbia River, hitting especially hard in population areas such as Portland and Vancouver, as well as Washington’s Tri-Cities.
As an example, with the storage dams protecting downstream locations, flood stage at Vancouver is currently at 16 feet elevation. However, without the storage provided by Canadian, Grand Coulee and John Day dams, flood levels could reach 25 feet in elevation, a full 10 feet above flooding today, and the high flows could last as much as a week longer, Barton said.
The Corps hosted two virtual updates specifically focusing on flood risk management, Dec. 4 and Dec. 5. Recordings of the sessions are here: https://www.nwd.usace.army.mil/crwm/columbia-river-treaty/
In its announcement for the virtual sessions, the Corps said that since signing the AIP, both countries have been developing how to proceed with a modernized Treaty regime. Until the new regime is in force, the two countries will be in an interim period in which the Corps has worked with Canada to secure the 3.6 MAF of preplanned flood risk management storage for 2025.
“If U.S. FRM (flood risk management) reservoirs and the 3.6 MAF of preplanned space in Canada are insufficient to address U.S. flooding, the U.S. will exercise its right to ‘call’ Canada for additional space under the Columbia River Treaty,” the Corps said.
Other Impacts Downstream
Eric Rothwell of the Bureau of Reclamation said the flood control changes made in U.S. waters will have little impact on upper Columbia River tribal salmon reintroduction efforts, although it could have a small effect on scheduling and costs of those efforts when flows are higher, but the impacts should be limited.
However, the changes, including higher river flow, could impact the migration of juvenile and adult salmon and steelhead. Those higher flows coming across the border, Rothwell said, can often be reregulated and shaped. Higher flows resulting from 2025 Treaty operations could also increase total dissolved gas levels at some Columbia River dams that are higher than the 125 percent TDG limit. River temperature during the spring and early summer will likely not be affected, he said.
Although it has little to do with flood control management, the new Treaty agreement in principle will provide an additional 1.1 MAF of flow augmentation from Canada in the summer to support fish.
Resident fish in Lake Roosevelt could be adversely impacted during very low reservoir drawdowns.
Barton said that higher than normal seasonal flows will occur just a few days each year, but there could be a higher cost for barge transportation, especially when more tugs are added to each barge heading upstream as flows increase and the stronger current slows barge traffic. He added that “I do not anticipate that shipping will be interrupted with real time flood risk management.”
Rothwell said that deep drawdowns in Lake Roosevelt and at the John Day Dam could impact irrigation withdrawals. A drawdown could prevent or slow pumping water from Lake Roosevelt back up into Banks Lake for future use (pumped storage, irrigation and re-regulating Grand Coulee).
In addition, the reservoir behind John Day Dam rarely gets below the minimum irrigation level, but with a deep drawdown there could be a brief impact on irrigation pumping for agriculture, he said.
The drawdowns could impact recreational activities when lowered lake levels leave some boat ramps on Lake Roosevelt and the John Day reservoir high and dry, Rothwell said. In addition, some Native American cultural sites could be exposed in Lake Roosevelt during extreme drawdowns. In that case, they could be vulnerable to looting or damage from erosion.
The Inchelium-Gifford Ferry on Lake Roosevelt will likely realize significant impacts on scheduling during deep drawdowns, Rothwell said. While ferry outages are currently infrequent, with the drawdown they could be longer.
There will be no flood risk impacts in the Snake River as the dams are not affected by Columbia River risk management operations, said General Hannon. “Likewise, they (lower Snake River dams) have no storage aside from their operating pools, and thus have no bearing on the mainstem flood risk management,” he said.
Columbia River Treaty British Columbia website is at https://engage.gov.bc.ca/columbiarivertreaty/agreement-in-principle/
For background, see:
— CBB, August 9, 2024, Guest Column: Canada-U.S. ‘Agreement-In-Principle’ Sets Stage For More Balanced Columbia River Treaty, https://columbiabasinbulletin.org/guest-column-canada-u-s-agreement-in-principle-sets-stage-for-more-balanced-columbia-river-treaty/
–CBB, July 12, 2024, U.S., Canada Reach ‘Agreement-In-Principle’ For Modernized Columbia River Treaty; Assures Pre-Planned Flood Control, Rebalances Power Benefits, https://columbiabasinbulletin.org/u-s-canada-reach-agreement-in-principle-for-modernized-columbia-river-treaty-assures-pre-planned-flood-control-rebalances-power-benefits/
–CBB, Oct. 13, 2023, Without A New Columbia River Treaty Corps Will Need To Use ‘Real-Time’ Flood Control, Rather Than ‘Assured Storage’ In Canadian Reservoirs, https://columbiabasinbulletin.org/without-a-new-columbia-river-treaty-corps-will-need-to-use-real-time-flood-control-rather-than-assured-storage-in-canadian-reservoirs/
— CBB, June 30,2021, NW Lawmakers Send Letter To Biden Urging ‘White House Led Strategy’ On Columbia River Treaty, Seek Reducing ‘Canadian Entitlement’; Conservationists’ Letter Stresses ‘Health Of The River’ https://columbiabasinbulletin.org/nw-lawmakers-send-letter-to-biden-urging-white-house-led-strategy-on-columbia-river-treaty-seek-reducing-canadian-entitlement-conservationists-letter-str/
— CBB, June 16, 2023, New Agreements Give Canada’s Indigenous Nations Revenue Sharing From Benefits Of Columbia River Treaty, https://columbiabasinbulletin.org/new-agreements-give-canadas-indigenous-nations-revenue-sharing-from-benefits-of-columbia-river-treaty/
— CBB, May 24, 2023, Columbia River Treaty Negotiators Meet In Kelowna; Discuss Salmon Reintroduction, Flood-Risk Management, https://columbiabasinbulletin.org/columbia-river-treaty-negotiators-meet-in-kelowna-discuss-salmon-reintroduction-flood-risk-management/
— CBB, April 20, 2023, As Expiration Date Nears, U.S., Canada Pushing To Finish Columbia River Treaty Negotiations By June; Uncertainty Over Future Operations A Motivator, https://columbiabasinbulletin.org/as-expiration-date-nears-u-s-canada-pushing-to-finish-columbia-river-treaty-negotiations-by-june-uncertainty-over-future-operations-a-motivator/