With high water levels in rivers, lakes and reservoirs across the Columbia-Kootenay region and a record for the wettest month ever in Castlegar’s history, it was hard not to notice flood management efforts in B.C. and in the U.S. What led to this situation?

Following a pretty normal fall and early winter 2011, the March 2012 forecast for runoff volumes looked fairly average for most of the Columbia Basin. But then…March hit. Precipitation across the basin was two to four times normal, and snowpack increased by about 15 percent in four weeks. Discharges from tributary reservoirs began increasing in response to the forecasts of rising water volumes. BC Hydro began maximum releases from Kootenay Lake in mid-March. A cool, dry May slowed snowmelt and runoff, and water volume forecasts stabilized. And then… June. Rainfall records were broken in many parts of B.C., northern Idaho, and western Montana. Runoff volume forecasts increased sharply as the Kootenay Basin experienced three times the normal precipitation in June. Flood risk management operations swung into high gear throughout the Columbia-Kootenay Basins.

While 15 percent of the Columbia River Basin lies within Canada, it generally provides about 30 percent of the overall river water volume. In high runoff years such as 2012, the Canadian portion of the Basin provides nearly half of the overall runoff. Coordinated management of Columbia River Basin water flows is essential for the protection of communities in both B.C. and the U.S.

In early June, Libby Dam in the U.S. switched from managing flows for sturgeon to managing flood impacts at downstream communities in both countries (including Bonners Ferry, Creston, Kaslo, and Nelson). BC Hydro and the U.S. Army Corps of Engineers also coordinated, under the Columbia River Treaty, a surcharge (i.e. fill above the normal allowable level) of Koocanusa (Libby) Reservoir to assist in downstream flood management. At the same time, BC Hydro and FortisBC worked closely to maximize the discharge from Kootenay Lake; this kept the peak lake level in early July as low as possible.

Later in July, with continued high runoff conditions, the Arrow, Kinbasket, and Duncan reservoir levels neared full-pool, and close coordination by all parties was needed to manage the high reservoir levels and the high river flows at Trail, Genelle, Castlegar, Revelstoke, Meadow Creek, and other communities in the Basin. The B.C. Water Comptroller had earlier granted BC Hydro the right to surcharge (i.e. fill above the normal allowable level) the Kinbasket, Duncan, and Arrow reservoirs if necessary to manage downstream flood risks. BC Hydro made use of this flexibility to reduce peak river flows while balancing impacts around the reservoirs. 

This year’s record precipitation and very high inflows highlighted the value of coordinated water management to minimize flooding impacts. The speed and efficiency of the coordinated response within B.C. and between B.C. and the U.S. was aided by the working relationships that have evolved under the Columbia River Treaty and other water management agreements. There will no doubt be a number of lessons learned from the 2012 freshet – both for the Treaty operating Entities and for communities. These will be important because climate change experts predict more extreme hydrological events in the decades ahead.