Frequently asked water management questions

Water management is the changing of water levels and water flows (volume/speed) by human actions throughout the Rideau Canal. This is done by:

1. Collecting data;
2. Analysing this data using models and tools that guide us in making decisions about changing water levels and flows;
3. Adding or removing logs, or changing mechanized settings, in dams throughout the system.

Because these changes have an impact both upstream and downstream, as well as at the specific location where changes are made, water management must be approached on a total system basis.

Water is managed for several reasons including:

• Public safety including mitigation of flooding;
• Protection of:
  • environment, fisheries, wildlife habitats
  • water supplies
  • navigation
  • recreation
  • hydro generation

The complexities of these multiple and interconnected considerations dictate the need to monitor and manage water on a full time basis, continuously throughout the year.

Parks Canada Rideau Canal manages water levels on the Canal corridor and throughout the watershed with a few exceptions.
The Ontario Ministry of Natural Resources, local Conservation Authorities and hydro producers collaborate with Parks Canada.

Water levels and flows fluctuate for a number of reasons. Large amounts of rain, for instance, can cause lake levels to rise while extended periods of drought can have the reverse effect. Dam adjustments to re-balance water levels and flows may cause lakes to rise or drop while moving towards targets.

It is important to note that water levels are only one consideration and are intricately connected to flow rates. Certain flow rates are required at certain locations throughout the system to ensure water supplies and water quality are maintained. 

The lowering of water levels happens every year at the same time and is referred to as "drawdown". Water levels need to be lowered to make room for the precipitation that happens in the fall, winter and spring. In order to mitigate against flooding and optimize public safety throughout the interconnected system, lakes are lowered to make room for high inflows that are typical over the non-navigation seasons. Lakes in general are operated following a series of guidance curves.   

Lakes identified as cold water fisheries (Bobs Lake and Big Rideau Lake) have to be down by mid-October to protect the fish spawn.  If water levels are dropped after this time period there is a higher chance of having a negative impact on the spawn.

Drawdown is when water levels are lowered on the Rideau.

It's a complex process that takes into consideration storage capacity of the lakes on the system, timing of fishery spawning, requirements for flood mitigation, typical fall and winter precipitation levels, downstream typography including constrictions like narrow river beds or dams, and overall volumes and flow rates.

Some lakes were created by dams when the Canal was constructed, to be reservoirs to provide adequate storage of water to be released as required over the navigation season. There are two reservoir lakes (Bobs Lake and Wolfe Lake) and two reservoir/canal lakes (Upper Rideau Lake and Big Rideau Lake).

There are many factors that guide the timing for drawdown and these will vary from lake to lake.

Water levels in your lake may appear low or high for a variety of reasons. For example:

• During a typical summer the water stored from spring is gradually released to meet varying demands across the watershed influenced, in large part, by weather.
• On lakes with a broad surface and shallow depth, evaporative losses over summer months typically exceed rainfall gains and water levels can drop for this reason. Conversely, when rains are heavy or winds are strong, levels can rise.

In addition to these natural factors, water levels are altered by dam log changes, the size and number of logs, the number of spillways and the number of dams affecting a body of water – are water management tools used to keep the system at targeted levels.

Water management happens all year long. Dam controlled water level adjustments to your lake depend upon conditions across the entire waterway. Think of the management of water levels as a domino effect; water level adjustments in one body of water impact the next, and so on.

You can find information about water levels by visiting the Water levels web site.

The online Water levels report is typically updated daily, excluding weekends and holidays. 

Parks Canada has a system of water gauges, many of which are automated and produce data that tells us levels on various parts of the system. This is supplemented by many manual gauges, as well as data provided by Environment Canada on precipitation and weather patterns.

Historic data and seasonal patterns are also used as an important reference point. This data is then fed into a contemporary engineering water model and along with extensive waterway knowledge daily water changes are implemented accordingly.

The dictionary definition of freshet (a noun) is "a sudden overflow of a stream resulting from a heavy rain or a thaw." The term is used in reference to water levels rising due to melting snow and rainfall.

Crystals of flowing ice that form together into a larger mass are referred to as frazil ice (also known as slush ice because of its appearance).

Two contributing factors behind frazil ice formation are cold temperatures and high river flow, particularly in turbulent areas, like dams. The accumulation of frazil ice in winter and early spring can create a natural dam effect inhibiting the flow of water.

Smiths Falls upstream of Detached Lock is the most susceptible to frazil ice buildup.  

The term "flow-through" is used to describe a body of water whose levels are dependent on water flowing from an upstream lake. When flows into the lake are high, levels rise; when flows into the lake are low, levels decline.

Christie Lake is an example of a flow through Lake.