graph of water levels on Mississauga Lake
Current Parks Canada water level information can be found at Parks Canada – Water Levels for Mississauga Lake.

You can see our updates about water levels here.

How to Read the Chart

Water levels are measured by the Trent Severn Waterway (TSW) using a gauge located at the Mississagua Dam. The water level is measured in metres (m) above the sill plate of the east spillway of the dam.

There are four lines on the graph showing the long term average level (orange), the maximum level ever recorded (yellow), the minimum level ever recorded (purple), and the current year water level (blue).

The new Mississagua Dam has three spillways, with eight logs in the east spillway and 10 logs in the west and centre spillways. The top six logs in the centre spillway are adjusted throughout the year to manage lake levels and downstream river flows. Each full log has a height of 0.3 m and the water management team also has access to a half log to make finer adjustments to levels.

NOTE: While the water level of the lake is ‘controlled’ by the number of logs in the dam, it will rarely be exactly equal to the level of the topmost log in the dam. It is usual for there to be a ‘head’ of water of several centimeters above the top of the dam; it is also possible for the water level of the lake to drop below the level of the topmost log in the dam due to dam leakage and evaporation, or the recent addition of a stop-log.

Key reference points:

Sill plate level of east spillway 0 m
Height of standard stop-log 0.305 m
Height of dam with all 8 logs in place in east spillway (Full Level) 2.44 m
TSW Target level in Spring 2.44 m
TSW Winter set level – 2 logs in place in east spillway 0.61 m
Nominal water level fluctuation (per logs)1.83 m
Historic average annual fluctuation (per chart) 1.36 m


Current Water Level Data

The main source of water level information is from the Parks Canada/Trent-Severn Waterway website. They produce three important sets of information, the Water Level Graphs which are updated daily; the Water Management Update reports which are released periodically, particularly when conditions are abnormal or changing; and the Drawdown Forecast reports which are released weekly during the season when the lake level is being drawn down, which is normally from mid-July through to mid-October.

The Coalition for Equitable Water Flow (CEWF) is a volunteer organization representing the 35 reservoirs in the Trent Severn Waterway (TSW) in Haliburton County and Northern Peterborough County. Their website presents important water level information focused on the reservoir lakes, including the Mississagua chain of lakes, the largest single reservoir in the TSW. The CEWF site also includes several important reports and historic water level records since 2013 to allow comparison with recent experience. You can register on the CEWF website to receive email notifications whenever new information is posted.