The Executive of the Coalition for Equitable Water Flow (CEWF) has been in regular contact with the TSW Water Management Manager and we have been monitoring levels and flows. This spring we experienced a very smooth filling of the reservoirs from snowmelt and periodic rainfall events. By the May holiday weekend all reservoirs were very close to their full levels and flow-through lakes and rivers were seeing seasonal flows.
Since that point the TSW Water management team has been actively managing reservoir dams, including the Mississagua dam, to maintain close to full levels while avoiding overfilling. This has meant operations at most dams with logs being removed and then replaced. Logs were removed from Mississagua at the end of last week and we can expect more action in the next day or two. TSW has an extensive data monitoring system for precipitation, levels and flows. The data are analyzed and water management decisions are made on a daily basis by the team.
Now we are facing significant rainfall events at the time of year when the system is full and only active water management can avoid higher than normal levels and flood risk. We always point out that the TSW is not a flood control system. This is especially true at this time of year when the system is full.
As I write this note on Tuesday, June 7, we are experiencing a major event with a forecast for up to 60 mm more rainfall. In addition, another significant system is in the forecast for Thursday. Because the rainfall is over the entire Trent basin, the management of levels and flows is very complex with the goal of maintaining navigation on the waterway while mitigating flood levels elsewhere. The extreme rainfall is associated with thunderstorms and the result is variable rainfall amounts over different areas. Today’s extreme rainfall appears to be possibly more concentrated in the Upper Gull watershed. The Burnt River basin which has a very large downstream area without any dams to control the flow is always vulnerable to flooding and those conditions are likely in the next few days. That Burnt River flow also immediately impacts the Kawartha Lakes.
We can expect to see active dam operations throughout the system, including at Mississagua Dam, with the current weather patterns and the entire system near full levels. The Water management team is actively passing significant flows all the way down the system to lake Ontario. We can expect increasing flows in flow through lakes and connecting rivers like the Mississagua River.
The risk exists for some lakes to reach an overfill condition which may cause dock systems and other waterfront infrastructure to be impacted. Waterfront property owners should monitor the water level on their lakes through the TSW water levels website. Be prepared to secure any infrastructure which could float into the lakes.
Looking ahead, the continent-wide atmospheric circulation is such that Environment Canada’s long-range forecast includes a higher than normal risk of extreme storm events over the summer season. So we can expect to see action at our dams as levels and flows are managed through the summer.
– Ted Spence, CEWF Chair and CCA Lake Steward