As winter turns to spring, waterways across the Canada-United States border get a fresh influx of water in what’s known as the spring freshet, with water entering the system from snowmelt and rainfall. This year, basins managed or monitored by the IJC are seeing strong flows and flood risks from central continental regions to the west coast.
While there is major flooding in the headlines in Lake Ontario and on the St. Lawrence River, conditions are different in other transboundary waters this spring.
Water levels in the Red River and its tributaries – located in Minnesota, North Dakota and Manitoba -were on the decline as of April 11, as water managers worked to keep water levels lower in Winnipeg while keeping levels at or slightly below the natural flow upstream of their control structure. Environment and Climate Change Canada and the US National Weather Service are expecting above-average precipitation in the Red River. Coupled with soil moisture levels that are either at or above average, forecasters in North Dakota are giving a 50 percent chance of flood levels comparable to 2006, and a 25 percent chance of flood levels comparable to 2009. There have already been reports of flooding.
Above-average precipitation is expected in the Souris River basin as well, following a wet fall. The International Souris River Board declared flood stage conditions in February in anticipation of problems, giving the US Army Corps of Engineers authority to manage water levels on the US side – the river runs through Saskatchewan, North Dakota and Manitoba. Upstream in Saskatchewan, the fall precipitation was between 160-280 percent above normal between September and November. Snowfall was either at or below average in the upper Souris but well above average in the lower Souris, near the North Dakota border. Saskatchewan’s freshet ended with reservoirs at or near flood stage.
In North Dakota, localized flooding is taking place along the eastern arm of the Souris River and its tributaries, due to the heavy snowpack and later thaw compared to the western arm. Despite all the gates being open on water management structures and dams, the flooding has damaged roads and culverts throughout the eastern arm of the Souris. Flood reports also have come in along the Souris River in Manitoba. If weather conditions remain normal, there is risk of flooding downstream of Minot, according to provincial representatives. With high precipitation, the risk of flooding could be severe.
Water flows and levels within the Rainy River-Lake of the Woods basin – located in Ontario, Minnesota and Manitoba - have been high through the winter months and remain high for this time of year. On the Rainy and Namakan basins specifically, water levels are high but still within the rule curves set out by the IJC for water managers to follow.
Things are closer to business-as-usual on the western end of the continent. The St. Mary and Milk Rivers in Montana and Alberta are facing average to below-average water flows throughout their basins. As of April, the Osoyoos Lake Board of Control has found no evidence that a drought declaration is necessary in the transboundary waterway in British Columbia and Washington, as water levels on the lake are within the rule curves. The Kootenay Lake area saw significant snowpack and precipitation over the winter and into the spring, causing water levels in the Kootenay River – which runs through Montana, Idaho and British Columbia - to rise in March in anticipation of a potentially large snowmelt; some agricultural fields have flooded in Canada and the US in the spring.
On the eastern end of the continent, the St. Croix River in Maine and New Brunswick saw water flows near the long-term averages in early 2017, with a spike in mid-April due primarily to snowmelt and increased precipitation. This is a sharp contrast to the prolonged low-flow conditions seen in 2016. There also has been flooding reported around Lake Champlain in New York and Vermont, though high water on the Richelieu River has not caused any reported flooding in Quebec.