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1.0 Monahan Drain Catchment: Facts

1.1 General/Physical Geography


  • Ottawa: (45 km2; 100% of catchment)


  • The Monahan Catchment resides within an extensive physiographic region known as the Ottawa Valley Clay Plain. This part of the clay plain can be greater than 15 metres deep but is truncated to the north and west where Paleozoic bedrock outcrops at the ground surface. This sediment was deposited in the Champlain Sea after the last glaciation. In this catchment, the Kars Esker, a regional sand and gravel feature, is found beneath the clay plain and is oriented northwest–southeast
  • In this catchment, the clay plain and buried esker are underlain mostly by dolostone and some limestone from the Oxford, Gull River and Bobcaygeon Formations. In addition, several geologic faults may pass through the catchment


  • The ground surface ranges in elevation from approximately 125 masl near along Old Richmond Road to approximately 90 masl at the catchment’s outlet

Drainage Area

  • 45 square kilometers; occupies eight percent of the Jock River subwatershed, one percent of the Rideau Valley watershed

Stream Length

  • Monahan Drain and tributaries: 97 km

1.2 Vulnerable Areas

Aquifer Vulnerability

  • The Mississippi-Rideau Source Protection initiative has not identified any Significant Groundwater Recharge Areas (SGRA), Highly Vulnerable Aquifers (HVA) or Wellhead Protection Areas (WHPA) 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 Monahan Drain catchment

1.3 Conditions at a Glance

Water Quality

  • Surface chemistry water quality rating in the Monahan Drain catchment is rated as “Poor” at both monitored water quality sites for the 2010-2015 period. The scores are largely influenced by frequent high nutrient concentrations, bacterial pollution, occasional metal exceedances and elevated chloride levels
  • Instream biological water quality conditions in the Monahan Drain are unknown

Instream and Riparian

  • Overall instream and riparian condition for the Monahan Drain is unknown

Thermal Regime

  • Warm/cool water thermal guild supporting the Jock River fishery

Fish Community

  • Twenty-three species of recreational and bait fish

Shoreline Cover Type (30 m. riparian area; 2014)

  • Crop and Pasture (65%)
  • Settlement (14%)
  • Transportation (13%)
  • Woodland (6%)
  • Meadow-Thicket (2%)

Land Cover Type (2014)

  • Crop and Pasture (60%)
  • Settlement (22%)
  • Transportation (8%)
  • Woodland (7%)
  • Meadow-Thicket (2%)
  • Aggregate (1%)
  • Wetland (<1%)
  • Water (<1%)

Land Cover Change (2008 to 2014)

  • Crop and Pasture (-181 ha)
  • Woodland (-36 ha)
  • Meadow-Thicket (-4 ha)
  • Wetland (0 ha)
  • Water (+3 ha)
  • Aggregate (+8 ha)
  • Transportation (+59 ha)
  • Settlement (+152 ha)

Significant Natural Features

  • Stony Swamp Provincially Significant Wetland

Water Wells

  • Several hundred (~500) operational private water wells in the Monahan Drain Catchment. Groundwater uses are mainly domestic, but also include groundwater monitoring and testing, municipal and other public water supplies, livestock watering and crop irrigation and commercial and industrial uses


  • Sections of three bedrock quarry licenses within the catchment

Species at Risk (Elemental Occurrence)

  • Bobolink (Threatened)
  • Eastern Milksnake (Special Concern)

1.4 Catchment Care


  • Twenty-two stewardship projects undertaken (see Section 5)

Environmental Monitoring

  • Chemical surface (in-stream) water quality collection since 2003 (see Section 2)
  • Fish survey along the Monahan Drain (see Section 3.1.3)
  • Thirteen headwater drainage feature assessments in 2015 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 3.2)
  • Groundwater chemistry information is available from the Ontario Geological Survey for two wells located in this catchment

Environmental Management

  • Development along the Monahan Drain and in and adjacent to the Stony Swamp 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
  • Twenty active Permits To Take Water (PTTW) in the Monahan Drain catchment issued for ongoing construction dewatering and 1 active PTTW for nursery irrigation
  • Twenty Environmental Compliance Approvals and/or Environmental Activity and Sector Registrations in the Monahan Drain Catchment. Most of these approvals/registrations are for municipal and private sewage works and municipal drinking water systems, while others are for waste management systems, municipal or private water works, industrial sewage works and air emissions