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Understanding Muskoka's Watershed – Water control isn't flood control
Ah, spring. It’s a time of renewal and regrowth, brought on by spring showers and, sometimes… flooding.
This winter came with an abundance of snow and unseasonable rain. It had many residents concerned that once it finally released its hold of water there’d be a repeat of 2013’s 100-year flooding event, a mere six years later. And flooding always raises a chorus of “why didn’t they do something about it?”
“They” are the Ministry of Natural Resources and Forestry (MNRF), the government agency tasked with, among other things, regulating water flow in Muskoka. Its bible in that regard is the Muskoka River Water Management Plan (MRWMP), which was created in 2006 and which defines how water levels are to be managed via a variety of control structures, primarily dams and weirs.
There are 42 such structures in the Muskoka watershed – 29 of them owned and operated by the MNRF and one by the District of Muskoka, 11 associated with power facilities, and one that is privately owned. Of those owned by the MNRF, some are self-regulating and others can be adjusted by the addition or removal of stoplogs to manage downstream flow.
But that flow management is not flood management.
While the MRWMP is a water control guide, its purpose is not flood control. The solution to flooding might seem simple on the surface – let more water flow through the system – but, in practice, it’s not that straightforward.
“The Muskoka River watershed is a cascading system. Water managers must always consider what is happening upstream of the dam, such as the amount of snow, and what impacts may result downstream of the dam,” says Chris Near, a resource management supervisor for the MNRF’s Parry Sound District which includes the Muskoka watershed.
Earlier this year, water operators drew lakes down, as they do every year, in anticipation of water entering the system from the melting snow pack as well as rain. Thanks to an above-average snow water equivalent – the amount of water contained in the snow pack – lakes were drawn down further than usual.
But “there are limitations on both the amount of water that can be released downstream and how much water can be stored upstream without having adverse effects, including potential flooding,” notes Near. “When water inflows from precipitation or snow melt are too high, these adverse effects may not be avoidable.”
The MNRF monitors water levels daily, with water flow and depth being two of the factors used to determine what action it might need to take. Historical data provides comparison points to help inform that decision.
The MNRF uses its own data as well as that measured by other parties, like Environment Canada, when making decisions regarding water control.
Environment Canada publishes both daily and historical measurements on its website (https://wateroffice.ec.gc.ca/). “Real-time” data is published within about six hours of collection time.
Water levels are collected using digital sensors stationed across Muskoka and, based on models generated using historical data, those numbers can be used to determine the discharge or how much water is flowing past that point.
Periodically, Environment Canada staff will visit a site where there are sensors – the most northerly sensor in Muskoka is on the Big East River near Arrowhead Provincial Park, and there are others at Fairy Lake, the north branch of the Muskoka River near Port Sydney, the south branch of the Muskoka River near Baysville, and at Port Carling, Beaumaris and Bala – to do manual calculations to ensure that the model is still correct.
Karina Dykstra, a hydrometric Tech-nologist with Environment Canada’s Meteorological Service of Canada, is one of the people who takes those measurements.
With tools that use acoustic Doppler technology to measure the depth and the speed of the water that’s flowing, she can calculate how much water is flowing in the river.
In addition to water entering the system, flows can be affected by weeds or trees that have fallen into the river that can cause the water to back up, or due to changes in features like waterfalls or riffles, she says. When those changes are more permanent, the model can be adjusted to reflect current conditions.
It’s not just the MNRF and dam operators that use this data. It is used for bridge construction where high water levels and flow are important to know, and at sites like waste water treatment plants that are restricted in how much effluent they are allowed to release by how much water is flowing by.
Flow data is even watched by recreational users like canoers and kayakers, who monitor it to know when the best conditions will be.
“The MNRF uses the flow data to decide what they’re going to do with their end of managing the water levels, whether they’re going to pull logs or add logs to the dams,” says Dykstra, adding that they take manual measurements at the stations about every six weeks and rely on the sensors the rest of the time.
To determine whether the MNRF needs to make adjustments at a part-icular dam or series of dams, water levels are assessed in conjunction with other information, such as weather forecasts, current watershed conditions, previous dam operations both upstream and downstream, watershed characteristics for individual lakes, individual dam characteristics, and how each lake responds to various dam settings, says Near.
“In the spring, MNRF District staff connect with local waterpower operators on a regular basis for updates and information about dam operations,” says Near. “The Muskoka River Water Management Plan outlines water levels and flows to be maintained throughout the system, at various times of the year.”
That’s the important part to note: the plan is about year-round maintenance of water levels and flows, not just those that occur in the spring.
Across the province, water management planning arose as a response to the opening of Ontario’s electricity market to competition in 2001.
The plans, including the MRWMP, “establish normal operating conditions for both water-power facilities and water control structures within a limited geographic boundary,” notes Near, adding that while water-power production is one consideration, it must be balanced with other uses and interests of the system as a whole including fisheries and navigation.
“The goal of a water management plan is to contribute to the economic and social well-being of people of Ontario through the development of waterpower resources and to manage these resources in an ecologically sustainable way for the benefit of present and future generations,” says Near. “Local water power companies (Ontario Power Generation, Orillia Power Generation Corp, Algonquin Power Fund Inc., and Bracebridge Generation) worked with the Ministry of Natural Resources and Forestry to develop a water management plan for the Muskoka River watershed.”
In Muskoka, while the MNRF operates water control structures that are not for hydro production, the waterpower producers operate their facilities “run of the river” or based on the natural flow of the water, says Near, rather than using water control structures or holding bays to store water for prolonged periods of time, although sometimes short periods are permissible and specified in the plan. “As a result, run of river operations have less of an impact on flows/water levels,” he says.
Within the MRWMP, each water control structure has an individual operating plan “that outlines the specific water levels and flows for that structure, including target, normal and high/low water operating levels,” adds Near. “The dams within the Muskoka River Water Management Plan are operated year-round to manage water levels, with some dams requiring daily operation during certain times of the year (like) spring melt, thunderstorms.”
And while the MRWMP can help to mitigate flooding, it’s not intended to avert it completely. It’s also what helps to ensure that there’s enough water in the system for recreational purposes.
In February 2018, the MRWMP was amended based on the Ministry’s 2016 Maintaining Water Management Plans Provincial Technical Bulletin. Among those amendments was the removal of the plan’s expiry date, which had earlier been extended to 2021.
“Water management plans are long-term documents which may require periodic amendments to ensure that the plans remain current, implement adaptive management, and/or provide clarity and certainty on how water levels and flows are managed,” says Near. That doesn’t mean that it can’t be changed, though. Anyone can raise issues regarding the plan with the Ministry, which can look to amendments as one possible resolution.
But there may be changes to Muskoka’s watershed management on the horizon.
In August 2018, Ontario’s Ministry of Environment, Conservation and Parks (MECP) announced $5 million in funding for a Watershed Conservation and Management Initiative – and said it would match funding from donations and other levels of government up to an additional $5 million.
In a release issued at the time, the Ministry said, “By protecting this particular watershed and working with the local community, this initiative will help us develop a more comprehensive approach to watershed management, which can inform current actions and future development. The initiative will also respond to concerns raised by the community about projects such as the North Bala Small Hydro Project, which is proceeding subject to a number of permits and approvals in place that require the facility to operate in the most environmentally responsible way. This includes a water management plan that requires minimum continuous flow to protect water quality and aquatic habitat and to meet Lake Muskoka’s water level objectives.”
In follow up this spring, a representative from the MECP said the government “is in the process of establishing an advisory group that will engage local organizations, municipal representatives, Indigenous communities, and the broader community to identify priority projects that could form part of this initiative. We will be seeking the group’s input as we design the program. More details on the timeline for this initiative will be available at a later date.”
The initiative will address the environmental challenges facing Muskoka, including increased development pressures, flooding due to severe weather events, increasing nutrient loadings, shoreline erosion and algal blooms, and could include projects to identify environmental impacts and how best to manage them, enhance monitoring of the watershed and shoreline restoration, and upgrade septic systems and enhance septic inspections.
According to the MECP, “This initiative will help us develop a more comprehensive approach to watershed management in Muskoka that can be applied to other watersheds in Ontario. Effective watershed management is beneficial to everyone, especially at times when watersheds are facing pressures due to stresses such as increased development and flooding caused by severe weather events.”
So perhaps there’s hope for flood-beleaguered residents after all.
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