Background Report

The Muskoka Watershed Report Card presents the results of monitoring the health of the natural features of Muskoka’s watersheds. The 2010 Muskoka Watershed Report Card is the third report card for the area and the content, level of detail, and accuracy of these reports has evolved and will continue to evolve as new and better information becomes available.

Muskoka is in excellent natural condition: 94% of the watershed is in natural cover; water quality is much better than provincial guidelines for recreational use; and most wetlands are intact. However, changes in vegetation communities, habitat loss, and water quality are becoming evident. The opportunity exists now to develop and live within the limits of our natural features before many of the values that draw us to Muskoka are lost.

The objective of the Muskoka Watershed Report Card is to report on the ecological health of the watershed in order to provide some understanding of the success of our collective ability to live within the natural limits set by the watershed.

Over the years the report card has addressed such issues as human health, municipal action, stewardship, and drinking water. Although all these issues are important, there are other agencies working within the watershed that are better suited to addressing them and so these indicators will no longer be reported on in the Report Card. For example, the Simcoe Muskoka District Health Unit prepares a newsletter on air quality and the associated health impacts.

The term Muskoka watersheds refers to all watersheds lying totally or partially within The District Municipality of Muskoka and includes areas in Algonquin Park, the Township of Seguin and the Township of Algonquin Highlands.

The area covered by the Muskoka Watershed Report Card includes all of tertiary watershed 2EB (Muskoka River watershed) and the northern portion of tertiary watershed 2EC (Black River-Lake Simcoe watershed). These tertiary watersheds can then be subdivided into 20 quaternary watersheds.

Watershed Characteristics


For the most part, the evaluation has been conducted at a landscape level using remote sensing tools such as air photography and satellite imagery. Results are provided on both an aggregated and subwatershed basis. Current data do not facilitate site specific analysis.  As the analysis moves from a landscape level to a subwatershed level, the variation in watershed health becomes more evident.

The health of each subwatershed is important not only because people relate more strongly to their local watershed area, but also because each subwatershed requires natural areas to support local processes that serve the needs of local residents for the many ecosystem services and functions they provide.

Benchmarks are necessary if one is to measure progress towards goals, but Provincial or National benchmarks appropriate to the forested environment of Muskoka do not exist. It has been necessary to develop benchmarks that are appropriate to our environment. Where a local standard has been developed and is generally accepted, it has been used. Where no standard has been established, the Muskoka average value has been used as the benchmark.


LAND

Indicators of the health of our land include:

◊ Percent of each subwatershed in natural cover. Natural cover is defined as
   lakes, wetlands, forests, rock barrens and other natural systems.

◊ Percent of each subwatershed in large natural areas. Large natural areas are
   defined as areas of forest, barrens, small lakes, and wetlands with a contiguous
   area of 200 ha or greater.

◊ Percent of each subwatershed in interior forest. Interior forest is defined as a
   forested area with a 100- metre forest buffer surrounding it. A healthy forested
   landscape should also have a percentage of interior forest with a 200-metre
   forested buffer.

◊ Percent of each subwatershed in protected and managed areas. Protected
   areas are defined as lands within national or provincial parks, Crown
   conservation reserves, Crown land, and land held by land trusts. Managed areas
   are defined as lands under the Managed Forest Tax Incentive Program or
   Conservation Land Tax Incentive Program, or have a conservation easement
   held by a reputable conservation organization.

◊ Percent natural riparian areas. Riparian areas are defined as the shoreline of a
   lake or river plus an area 20 metres inland from the shore.

The terrestrial component of each subwatershed can be analyzed based on these five components. Together they provide an indication of the health of the terrestrial component of the watershed.

Overall Subwatershed Grades for the Land Component of the 2010 Report Card



WATER

Water quality is one of the fundamental components of a healthy watershed. As people live and work around lakes, they impact and change the lake ecosystem. Some of these changes may be beneficial and others may degrade the natural systems upon which both humans and other species rely.

The Muskoka Watershed Report Card grades the health of our lakes using the following indicators:

◊ Percent of lake surface area in a watershed that is Over Threshold for Total
   Phosphorus. This is a measure of recreational water quality, as phosphorus is
   generally the limiting nutrient in algae production.

◊ Percent natural shoreline is an indication of good fish habitat. Many fish species
   require overhanging vegetation, rock shoals, and aquatic vegetation found in
   undisturbed sites.

◊ Mercury levels in fish are an indicator of a contaminated aquatic environment.
   Mercury levels in lakes do not pose a significant human health threat; however,
   wildlife like loons are less tolerant of mercury and may be impacted in some
   cases.

The aquatic component of each subwatershed can be analyzed based on these three indicators. Together they provide an indication of the health of the aquatic component of the watershed.

Based on work undertaken within Muskoka, local benchmarks have been developed against which change in the watershed can be measured. The 2009 benchmarks will be used in future report cards to understand change within the watershed.

Overall Subwatershed Grades for the Water Component of the 2010 Report Card



WETLANDS

In southern Ontario, ecologists recommend that 10% of a watershed should remain as wetland in order to provide the ecosystem services and functions necessary for a healthy watershed.

However, on the Canadian Shield this figure is less applicable. In Muskoka, many subwatersheds are naturally comprised of less than 10% wetlands.

Therefore, for the purpose of the Report Card, it is assumed that the current wetland area in each subwatershed is close to its natural level. For example, Skeleton Lake subwatershed has only 5.7% wetlands and the Lakes Rosseau and Joseph subwatershed has only 6.46% wetlands. As a result, these lakes are clear, cold water lakes that support healthy lake trout populations.

A value of no net loss of wetlands from the 2010 level will be used as the benchmark. In future report cards, wetland area will be measured as a deviation from current wetland areas as determined by a landscape level evaluation using air photography.


SUMMARY

The health of a watershed can be defined both scientifically as the ability of a system to continue to provide ecosystem services and functions, and sociologically as the level of ecosystem function that is acceptable to society.

Human settlement and activity are part of the watershed and future development is not only inevitable but also necessary to ensure the vibrant nature of communities.

Whereas it may not be appropriate to hold a more developed subwatershed – such as the subwatersheds that encompass the Towns of Bracebridge, Huntsville and Gravenhurst – to the same high standard as an undeveloped subwatershed, more science is required to establish appropriate benchmarks that define a balance between the built and natural environments.

Overall Subwatershed Grades for the 2010 Report Card



CLIMATE CHANGE

Perhaps the biggest challenge facing the watershed is climate change. Between 1948 and 2006 Ontario’s average temperature increased by 1.3 ⁰C. Projections made by the Ministry of the Environment indicate average temperatures over the Great Lakes Basin, which include Muskoka’s watersheds, are likely to continue to rise between 2 and 4 ⁰C by 2050.

The Ministry of the Environment goes on to predict that precipitation may increase by up to 20% by 2050 in all but the summer months, when little or no change is projected. Rising air and water temperatures are already shortening the ice cover season, exposing water to evaporation for more of the year.

Even if carbon emissions ended today, the global temperature would continue to rise through to the end of this century.

Adaptation to a modified climate is necessary. Maintaining natural areas and enhancing the health and diversity of ecosystems is essential to the long-term sustainability of watersheds that will be threatened by climate change.

Climate Change and Adaptation in Muskoka paper