Upper Thames River watershed in Low Water Situation (media release, May 11, 2021)
The Upper Thames River watershed is experiencing Level 1 Low Water conditions, according to the local Low Water Response Team. The Level 1 advisory is part of a three-tiered system used in Ontario to inform the public of local low water conditions.
“We evaluate low water conditions by looking at several indicators, including precipitation and stream flows,” said Mark Helsten, Senior Water Resources Engineer with the Upper Thames River Conservation Authority (UTRCA).
The watershed received an average of 51 mm of precipitation in April, which is about 61% of the long term normal for that month. Precipitation over the past three months (February – April) was about 46% of normal. Over the past 18 months (November 2019 – April 2021), precipitation measured by Environment Canada at the London Airport was about 86% of normal. Stream flows across the watershed are also below normal for this time of the year.
The unusually dry spring is impacting water levels in some of the UTRCA’s reservoirs. The Conservation Authority maintains three large reservoirs and several smaller ones across the watershed. Two of the large reservoirs – Pittock and Wildwood – provide flow augmentation in the summer as well as flood control year round.
“We hold back some of the spring runoff to raise the reservoirs to their target summer elevations,” said Helsten. “This year, Wildwood Reservoir is still about one metre below its summer target elevation, but we’ve been able to fill Pittock Reservoir and hopefully we can maintain it at that elevation until mid-June when we begin to release water and augment flows downstream.”
Wildwood Reservoir, which is on Trout Creek upstream of St. Marys, is traditionally more difficult to fill than Pittock, which is in Woodstock.
Two small recreational reservoirs that are lowered in the fall and filled in the spring are RT Orr Reservoir in Stratford and Mitchell Reservoir in Mitchell. Orr Reservoir was filled earlier this season and has reached its target summer level. Mitchell Reservoir is usually filled a couple weeks after Orr and has yet to be filled due to the dry conditions.
The Low Water Response Team encourages people, businesses, and industries that rely on local surface water or groundwater to conserve water. Many watershed municipalities have water conservation programs in place.
The City of London and some other communities take water from Lake Huron and Lake Erie. Reducing water use in these communities will not improve flows in the Thames River or its tributaries.
Contact: Eleanor Heagy, Communications Specialist