RVCA Report Reveals Water Quality Variations in Frontenac Lakes

Jeff Green | Mar 06, 2024

As reported in the Frontenac News in February, the Rideau Valley Conservation Authority (RVCA) released a comprehensive watershed conditions report in February. With assistance from Emma Jackson at RVCA, we were able to obtain some of the sub-watershed data from the report to look at the section of the Rideau Waterway that is located in Central and South Frontenac.

“The report’s common themes also apply to Frontenac’s townships,” said Emma Jackson, “loss of wetland and headwater drainage, increasing development, and lack of adequate stormwater management and runoff reduction which can all impact local surface water quality and increase risks of floods and erosion.”

The reports drills down to the subwatershed level , providing detail about water quality and other matters on specific lakes. The subwatersheds and their corresponding catchments most relevant to our readers are the Tay River subwatershed and the Rideau Lakes subwatersheds.

The headwaters of the Tay River Watershed include feeder streams and lakes that into Bobs and Crow lakes, extending to Bolingbroke, where water levels for Bobs and Crow, and points downstream, are managed. The western edge of the Rideau Lakes Watershed is located in Bedford District of South Frontenac, near the Village of Westport.

One of the key sections of the report for Frontenac County in particular, are the water quality reports for lakes and creeks in Frontenac County. Some of the head water lakes, such as Carnahan, which is near Long Lake in the Parham area, and Elbow Lake, which feeds Fish Creek, are considered “tea stained lakes” because they are high in organic matter, score lower on the Water Quality Index (WQI) than other lakes. “They are just generally and naturally more nutrient rich,” said Jackson, so it is not necessarily alarming that they score lower on the water quality index.

“As the water moves towards the Tay and towards Bobs Lake, we have fairly consistent water quality conditions,” she said.

The report includes charts detailing water quality scores for the upper watershed lakes over time, and shows that most of the lakes are within the green zone (water quality protected with only minor threat) or the yellow zone (water quality is usually protected but occasionally threatened or impaired).

As an example of the detailed analysis used by RVCA in preparing the report, Bobs Lake is divided into 10 sections to account for all of the bays and narrows in the lake. While most of Bobs Lake is in the Green zone, Mill and Mud bays are in the yellow zone. Crow Lake and Leggat Lake are also in the yellow zone.

“Loss of wetland and headwater drainage, increasing development, and lack of adequate stormwater management and runoff reduction, which can all impact local surface water quality and increase risks of floods and erosion,” Jackson said.

One of the key findings of the report, and this was true for rural areas in particular, was that groundwater quality monitoring is often lacking, which is a concern because in many cases groundwater is the main source of drinking water.

“This is true both in the pre-development stage (when the developer has an opportunity to identify drinking water quality issues before development begins) and once the area is inhabited, either by residents or businesses,” said Jackson.

“Also, residents generally do not test their drinking water routinely at the recommended intervals, and rarely test for more than bacterial contamination, which does not give the complete picture,” she added.

Many areas of the watershed also have naturally occurring metals, minerals and contaminants in the local groundwater, and almost all of the watershed is vulnerable to human-introduced contaminates from septic, roads, agriculture, industry and other land uses due to its exposed bedrock and thin soil cover.

In terms of land use and land use changes over time, the story is pretty similar in both South and Central Frontenac, and it is a relatively healthy picture in terms of watershed sustainability.

The amount of both woodlands and wetlands have increased slightly since 2008, 1.4% for woodlands and .3% for wetlands, while pasture and meadow lands have decreased. In the Central Frontenac section, pasture land has decreased by 15% between 2008 and 2020, and has decreased by 11% in the South Frontenac section. This might reflect trends in beef cattle operations, which continue to drop off across the Canadian Shield landscapes in Frontenac County. The number of roads and settlement areas have increased over that time in both South and Central Frontenac. Settlement areas are up by about 6.5% in both townships.

But while the land used for aggregate production was flat in Central Frontenac, it was up by over 8 hectares (20 acres) in the South Frontenac section, an increase of over 34%.

The entire watershed report is available at rvca.ca, by typing watershed conditions report into the search bar at the top right hand side of the index page.