Regular rainfall needed to boost lake and river levels
By Jenn Watt
Water levels on some of the area’s reservoir lakes may drop as much as 25 centimetres during the Trent Severn Waterway drawdown, conducted over a two-week period, which started last week.
According to Parks Canada’s water management update on June 30, lakes in the Haliburton area, which feed into the TSW, were at or below long-term average levels with Gull River reservoirs at 92 per cent full, Burnt River reservoirs at 91 per cent full, and central reservoirs at 94 per cent full.
Ted Spence, chair of the Coalition for Equitable Water Flow, said the drawdown is a usual occurrence for this time of year, but normally the region would have received far more rain.
“What’s not normal is that it has been so dry and there’s not very much water coming into the system. Normally, they would be drawing water from the system … but there’d also be quite a bit coming in from rain, from normal rainfall, and runoff from rivers and streams into the lakes,” he said in an interview on July 3.
On July 7, the fire chiefs of Haliburton County issued a fire ban due to consistently dry conditions.
Rainfall for the region has been between 25 and 50 per cent below normal for May and June.
Spence pointed out that the flow on the Otonabee River in Peterborough has already been reduced to its minimum.
“If you go down to the Kawartha Lakes, there’s very little water moving from lake to lake. They’ve got the flow as low as they can get it and still maintain the water supply and the water quality minimums for the Peterborough area,” he said.
According to an update from CEWF, in addition to the dry conditions in May and June, the snowpack melted early for the reservoir lakes.
“This spring the snowpack was normal in March but it melted very early with peak flows in late March and early April. In order to protect against the risk of flooding from extreme spring rainfall events like have occurred in several recent years, the TSW water management team adopted the strategy of only filling reservoirs to 90 per cent of full and then allowing levels to come up with spring rainfall. Because of the dry spring many reservoirs did not get to their full levels or close to full until mid or late June,” the update reads.
The dry conditions are something to keep in mind, Spence said, but they should not be creating major issues for waterfront property owners yet.
“Nobody’s anywhere near having a problem with a waterline or anything like that,” he said.
The region is experiencing the type of weather projected in climate change models: extreme events and more variability (floods and droughts), he said.
“The other notable thing right now is that the dry conditions extend all the way from Haliburton to Lake Ontario, so the Trent Severn water managers aren’t dealing with a situation where they don’t have a problem down in the south. They have limited water supply over the whole system and the rain is not replenishing the lakes,” Spence said. “The other thing that happens of course is on the big lakes as the water gets warmer with these long days and all this sunshine, is an awful lot of evaporation. That’s especially true on the big lakes.”
Updates from CEWF on TSW water management can be found at https://cewf.typepad.com/