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1.0 Otty Lake Catchment: Facts

1.1 General/Physical Geography

Drainage Area

52.8 square kilometres; occupies 6.6 percent of the Tay River subwatershed; 1.2 percent of the Rideau Valley watershed.


The Otty Lake catchment resides within part of the physiographic region known as the Algonquin Highlands. In the Tay River Subwatershed, this ancient and hilly geologic region is made up of such Precambrian rocks as marble, conglomerates, and dark or colour banded granite-like rocks. A large area of younger sandstone flanks the catchment’s northern boundary. A veneer of glacial drift (glacial till, sand etc.) overlies the bedrock.

Municipal Coverage

Drummond/North Elmsley Township (18.7 km2; 35.4% of catchment)

Tay Valley Township (34.0 km2; 64.4% of catchment)

Town of Perth (0.1 km2; 0.2% of catchment)

Stream Length

All watercourses (including headwater streams): 98.6 km.

1.2 Vulnerable Areas

Aquifer Vulnerability

The Mississippi-Rideau Source Water Protection program has mapped the north boundary of this catchment as a Significant Groundwater Recharge Area and all of the catchment as a Highly Vulnerable Aquifer. There are no Well-Head Protection Areas in the catchment.

Wetland Hydrology

A watershed model developed by the RVCA in 2009 was used to study the hydrologic function of wetlands in the Rideau Valley Watershed, including those found in the Otty Lake catchment.


1.3 Conditions at a Glance

Fish Community/Thermal Regime

Warm and cool water recreational and baitfish fishery with 19 species observed in Jebbs Creek during 2016.

Headwater Drainage Features

Primarily classified as wetland and natural features with minimal modifications.  

Instream/Riparian Habitat

Jebbs Creek: Low to high habitat complexity with increased habitat complexity observed in the lower and upper reaches of the system within the catchment along with a healthy diversity of plant types and levels throughout the surveyed sections; however, there are areas of extensive plant growth (64 percent) which are dominated by the invasive aquatic plant, European frogbit. Dissolved oxygen conditions in Jebbs Creek vary along the system for both warm and coolwater fish species.

Land Cover Change (2008 to 2014)
Catchment Woodland Crop-Pasture Meadow-Thicket Settlement
Hectares -7 -3 -1 +11
Land Cover Type (2014)
Catchment Woodland Wetland Water Crop-Pasture Settlement Transportation Meadow-Thicket
Percent 41 21 14 13 5 3 3
Shoreline Cover Type (30 m. riparian area; 2014)
Catchment % Jebbs
% McLaren
% Otty
% Streams* %
Wetland 44 Wetland 83 Woodland 51 Woodland  48 Wetland 51
Woodland 37 Woodland 10 Wetland 49 Settlement 35 Woodland 32
Settlement  8 Settlement 5 --- --- Wetland 14 Crop-Pasture 12
Crop-Pasture  8 Transportation 1 --- --- Transportation 3 Transportation 2
Transportation  2 Crop-Pasture 1 --- --- --- --- Settlement 2
Meadow-Thicket 1 --- --- --- --- --- --- Meadow-Thicket 1
*Excludes Jebbs Creek

Significant Natural Features

Tay Marsh Provincially Significant Wetland

Tay Marsh Regional Candidate Area of Natural and Scientific Interest, Life Science.

Species at Risk (Elemental Occurrence)
Species at Risk Status
Blanding's Turtle Threatened
Black Tern Special Concern
Eastern Milksnake Special Concern
Eastern Musk Turtle Special Concern
Northern Map Turtle Special Concern
Snapping Turtle Special Concern
Water Quality for the Protection of Aquatic Life
Water Quality Source Jebbs Creek McLaren Lake Otty Lake
Surface Chemistry Good Poor to Fair Fair to Good
Instream Biological Poor to Fair --- ---

Jebbs Creek: Benthic invertebrate samples are dominated by species that are moderately to highly tolerant of high organic pollution levels.

Water Wells

Approximately 620 operational private water wells in the Otty Lake catchment. Groundwater uses are mainly domestic.

Wetland Cover

Wetlands are reported to have covered 31 percent of the Otty Lake catchment prior to European settlement, as compared to 21 percent (or 11.1 square kilometres) of the area in 2014. This represents a 31 percent (or 5.0 square kilometre) loss of historic wetland cover.Fourteen percent of the remaining wetlands are regulated leaving 86 percent (or 9.5 square kilometers) unregulated.

1.4 Catchment Care

Environmental Management

The Otty Lake Association prepared the Otty Lake Management Plan (2008) to provide a summary of what is known about the Otty Lake catchment along with the community’s vision for the lake and a list of its main concerns and actions to address them. This has been followed-up with the release of the Otty Lake Five-year Review (2014) and annual State of the Lake Reports initiated by the OLA in 2014, which is a comprehensive report providing information regarding water quality, the lake fishery, wildlife habitat, shoreline planting initiatives, the amounts of zebra mussels and algae, among many other topics.

Development along Jebbs Creek (Rideau Ferry Road to the Tay River) and in, and adjacent to, the Tay Marsh Provincially Significant Wetland in the catchment is subject to Ontario Regulation 174-06 (entitled “Development, Interference with Wetlands and Alterations to Shorelines and Watercourses”) that protects the hydrologic function of the wetland and also protects landowners and their property from natural hazards (flooding, fluctuating water table, unstable soils) associated with them.

Three Environmental Compliance Approvals were sought in the catchment for waste management sites and an industrial sewage works.

Environmental Monitoring

Chemical surface (in-stream/lake) water quality collection by the RVCA since 2003; prior to this date, the Otty Lake Association has coordinated/undertaken other chemical water quality analysis (see Section 2 of this report).

Benthic invertebrate (aquatic insect) surface (in-stream) water quality collection by the RVCA in Jebbs Creek since 2005 (see Section 3.3.1 of this report).

Fish survey and stream characterization survey by the RVCA on Jebbs Creek in 2016 included taking measurements and recording observations on instream habitat, bank stability, other attributes and preparing a temperature profile (see Section 3 of this report).

Otty Lake shoreline assessed as majority regenerative (236 properties; 49 percent); majority ornamental (172 properties; 36 percent) and majority natural (74 properties; 15 percent) by the Love Your lake Program.

Thirty-two drainage feature assessments were conducted by the RVCA in 2016 at road crossings in the catchment. The protocol measures zero, first and second order headwater drainage features and is a rapid assessment method characterizing the amount of water, sediment transport, and storage capacity within headwater drainage features (see Section 3.4 of this report).

Classification of Otty Lake catchment land cover types derived by the RVCA from colour aerial photography that was acquired during the spring of 2008 and 2014 (see Section 4.1 of this report).

The Mississippi Rideau Septic System Office has conducted 348 mandatory septic system re-inspections on 250 properties around Otty Lake from 2012 to 2017 and nine voluntary septic system re-inspections on seven properties around McLaren and Mud Lake from 2004 to 2017 (see Section 5.5 of this report).

Groundwater chemistry information is available from the Ontario Geological Survey for one well (#13-AG-022) located in the catchment


Sixty-four stewardship projects were completed by landowners with assistance from the RVCA (see Section 5 of this report).