Water Level Woes

Why did many lakes in Muskoka experienced extremely low water levels this summer? The short answer is that the low water level was due to a combination of low snowfall over the winter of 2012, lack of rain and high temperatures with lots of sun this summer (creating a net loss through evaporation), and the need to manage water levels up and down the Muskoka River system.

Between the variables we can control and those we can’t, Mother Nature seems to have had the upper hand this year.

For example, Lake of Bays is controlled by a dam at its outlet in Baysville which empties into the south branch of the Muskoka River. The management of the dam by the Ministry of Natural Resources (MNR) is governed by the Muskoka River Water Management Plan, which requires a minimum flow of 3 cubic metres/second, so closing the dam completely (i.e. no discharge) is not an option.

The MNR reports that logs were placed at the dam to maintain the minimum level of outflow as early as the beginning of July. By August, Lake of Bays was 18 cm below its operating target and many lakes in the area were down 25 cm. The lakes that feed into Lake of Bays (Smoke and Tea Lakes in Algonquin Park and Kawagama Lake in Algonquin Highlands) were low even in early spring, resulting in less water going into Lake of Bays than usual.

You may have wondered why water levels on Lake Muskoka were close to normal this year compared to the low level higher in the watershed. Many people questioned if too much water was sent downstream too early.

According to the MNR, Lake Muskoka is supplied with water from a much larger catchment area than Lake of Bays (4,683 km² for Lake Muskoka compared to 1,481 km² for Lake of Bays), so there is more water flowing into Lake Muskoka.

In addition, Lake Muskoka experienced more rainfall than Lake of Bays last summer according to the MNR’s weather stations, one of which is in Lake of Bays. Lake Muskoka water levels came up nicely in August after a significant rain event which appeared to miss the Lake of Bays area.

Usually, a fall drawdown of water on Lake of Bays commences after the first week of September to lower water levels for lake trout spawning. This year, however, water levels reached the fall drawdown target by late summer. The MNR reports that no intentional drawdown will be initiated in Lake of Bays and other lakes for the 2012 season unless there is significant rain this fall.

Is this just a one year phenomena or can we expect more years of low water levels? With our changing climate we don’t know. Each year water managers will have to second guess what Mother Nature is going to give us and act accordingly.

Past articles are available in this blog under the Watershed Notes Articles category or under Past Articles in the Resources section.