Water Level Forecast – July31/18

Significant Rainfall Over the Reservoirs has Reduced the Risk of Extreme Low levels

As of July 31, TSW released a new Water Management Update (click here) as well as a new Drawdown Forecast (click here) for the reservoirs.

During the past week the reservoir area in Haliburton and Northern Peterborough County has received 50 mm (2 inches) of rainfall or more. With the thunderstorms the local amounts have varied but all areas have had significant relief from the drought of the last three months.

Until the past week, 2018 was shaping up to be an extremely dry spring and summer with a worse drought than in 2016.

In the face of low rainfall and very high evaporation rates from large lakes, the TSW water management team have done an excellent job of conserving water throughout the system such that reservoir levels have been at about average levels for late July. The flows on the Otonabee River and Trent River have been at minimum levels. But evaporation losses from the large lakes have been very high. A week ago we were facing a more rapid drawdown of the reservoirs if the recent rains had not come.

May was a very dry month until 25mm (1 inch) of rain was received on the 31st. Overall the rainfall deficit in May was 15%. June then saw a rainfall shortfall of 25%. Then July through the 22nd recorded a shortfall of 90% with only 9mm falling compared to a normal July with 90mm. Fortunately in the last week we have received 50mm (2 inches) or more of rainfall. Although it still looks like the July total will be about 30% below normal the rains have provided a cushion allowing the drawdown to be slowed with the expectation that reservoir levels will be close to average at least  in the immediate future when more regular rainfall events are in the forecast..