SATURDAY, AUGUST 28, 2021 11:23 a.m. – The level of Lake Saint-Jean has been particularly low since the beginning of August, making a place for itself among the most worrisome of the past 70 years.
The level is expected to reach 12.6 feet during the month of September.
It would also be the fourth lowest water level since 1953.
A series of unfavorable weather conditions paint a watercolor picture of the driest of the 70 years.
The watershed of Lac-Saint-Jean is very large, covering an area of approximately 70,000 square kilometres. The main rivers flowing into Lake Saint-Jean are the Ashwapmuchuan, Mystacini, Pripunca and Metapchoan, which account for nearly 90% of the lake’s water supply, According to the Lac-Saint-Jean watershed organization.
Each of its rivers is experiencing a lower level than usual, and this fact has an impact on the lake: the latter is already the main outlet for its region. So the water shortage is felt throughout this vast area.
The spring flood was modest and very early due to the mild spring season. The lake stopped on April 16 for the first time since 1945. This reduced the water supply that Lac-Saint-Jean generally benefits from at this time of year.
Then solve the drought. Thus the rivers feeding the lake were not able to compensate for the deficit accumulated during the spring.
July eased the drought trend a bit: Roberval actually got 108.6 mm of water during the month, versus a monthly average of 115 mm.
August however carried the torch of drought. Roberval only had about twenty millimeters of water, while the normal figure is about 101 millimeters for the whole month. The result: the lake level can reach 13 feet until the end of August, and drop further until the beginning of September.
A similar scenario in Quebec
The rest of Quebec was not spared a noticeable drought during August. All of southern Quebec, with the exception of the Gaspé tip, suffers from a significant rainfall deficit.
The most obvious example is in the northwest of the province: Abitibe-Tmiskaming’s rain has accumulated barely 2 mm since the beginning of August, versus 80 mm on average. A similar situation also occurs in Montreal, where nearly twenty millimeters of water have fallen since August 1.
And while rain over the next couple of days is likely to soften the picture, there is no indication that it will be enough to make up for the significant shortfall.
Remember that a low pressure system will invade Quebec between Saturday and Monday, bringing good rain and a risk of thunderstorms in its wake.