Subwatershed Reports

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1. Catchment Facts

General Geography

  • The Rideau River flows through the heart of the Middle Rideau and is a focal point for residents and visitors to the area. It extends from the outlet of Lower Rideau Lake at Poonamalie (where there is one dam and one lock) to Burritts Rapids (where there is also a dam and lock), at which point it enters the Lower Rideau on its way to Rideau Falls. The Rideau River is also an integral part of the Rideau Canal National Historic Site of Canada and is a significant tourist attraction which draws boaters, cottagers, and campers to the area
  • Smiths Falls, Merrickville and Burritts Rapids are the main urban settlements in the Middle Rideau subwatershed. The Rosedale Creek catchment is predominantly rural in character with agriculture being the main land use
  • Parks Canada staff manage water levels for recreational purposes along the Rideau Canal/Waterway that flows by the catchment, ensuring 1.5 metres of draft during the navigation season. In this managed system, water levels on the Rideau Canal are manipulated by operation of numerous dams. In the Middle Rideau subwatershed, Parks Canada staff operate 9 dam and lock complexes with 13 locks for a fall of 36.2 metres over 35.6 kilometres. Water levels are maintained as close as possible to set objectives through the May to October navigation season. The levels are lowered through the rest of October and into November and held at the winter levels until the spring freshet in late March or early April naturally increases inflows to the system. To reduce the impact of the higher flows in the spring, the amount of snow water equivalent, forecast rain, ice cover, flows and levels are assessed and the dams in the Middle Rideau reach are operated accordingly to quickly pass as much water as possible. In late April and early May, the dams are gradually closed and water levels are brought up to be ready, once again, for the navigation season

Physical Geography

  • All of Rideau Creek Catchment and the rest of the Middle Rideau Subwatershed primarily resides within the Smith Falls Limestone Plain. The northern half of this catchment is underlain by older Paleozoic quartz sandstone and dolostone of the March Formation; while the southern half is underlain by Oxford Formation dolostone. The bedrock in the catchment is overlain by a thin veneer of glacial sediment, referred to as ‘drift’ that is generally less than a metre in thickness; although there are organic deposits underlying the large headwater wetland and clay lining the corridor of the main creek
  • One hundred percent of the catchment lies within the Township of Montague
  • Rideau Creek catchment drainage area is 68 square kilometres and occupies about eight percent of the Middle Rideau subwatershed and two percent of the Rideau Valley watershed

Vulnerable Areas

  • Lower reach of Rideau Creek is subject to a flooding hazard during the regional storm flood (the 100 year flood). Surveys and studies undertaken in accordance with provincial standards have determined that the 100 year flood elevation in this area ranges from 91.4 metres above mean sea level at the upper, mapped extent of the regulation limit above Heritage Drive to 89.3 metres above mean sea level at its outlet to the Rideau River
  • The Assessment Report developed under the Ontario Clean Water Act identifies the upper bedrock aquifer underlying all of the catchment area as a Highly Vulnerable Aquifer, although, where sediments are thicker in a local area, the vulnerability would be less. The southern half of the catchment lies within part of the Wellhead Protection Area for the Merrickville municipal wells; related provincial policies may apply

Development/Trends

  • The Township of Montague consists of scattered residential and agricultural development, mostly along traditional transportation routes and in areas of good agricultural capability. Commercial and industrial development is very limited outside the settled areas and there are no major employers within the Township
  • Recent years have seen an increase in residential lot creation throughout the catchment, after a lengthy period of stagnant population. Montague's relative proximity to Ottawa and ease of access, as well as relatively affordable land are thought to have contributed to this. Interestingly, most recent severances have been in the more rural forested settings, as opposed to along major transportation corridors or established built communities. As such, site specific environmental impact studies and development conditions have often accompanied approvals. Lot sizes have often also been larger than the 'standard minimum' of an acre. Montague's population had one of the highest rates of increase among Lanark County municipalities between 2006 and 2011

Conditions at a Glance

Water Quality

  • Surface chemistry water quality rating in Rideau Creek is “Fair” over two reporting periods (2003-2008 and 2009-2014). Elevated bacterial counts and nutrient concentrations from inflows of nutrients (from private septic systems, agricultural and residential surface water runoff) are an occasional feature of Rideau Creek and decreased nutrient and bacterial counts are needed to improve the overall health of the creek
  • Instream biological water quality conditions at the Rideau Creek sample location range from “Poor” to “Good” from 2003 to 2014 (using a grading scheme developed by Ontario Conservation Authorities in Ontario for benthic invertebrates) with an overall benthic invertebrate water quality rating of “Poor” to “Good” determined for this period

Instream and Riparian

  • Overall instream and riparian condition for the Rideau creek catchment as assessed by the stream characterization and headwater drainage feature assessment programs show that Rideau Creek and its tributaries are in generally good condition. The majority of the system has a healthy riparian corridor with some sections having elevated erosion levels. Instream diversity of aquatic habitat is somewhat variable with low levels of riffle habitat and high levels of pool habitat. An opportunity was identified along Rideau Creek to enhance riparian habitat conditions. Three perched culverts were identified as migratory obstructions for fish passage
  • The Rideau Creek catchment has 21 species of recreational and bait fish and is classified as having a cold/cool/warm water thermal guild that supports the Rideau Creek/Rideau River fishery
  • In the Rideau Creek catchment, the riparian buffer (30 m. wide strip along the shoreline of all lakes and streams) is comprised of wetland (74 percent), woodland (15 percent), crop and pastureland (eight percent), roads (two percent) and settlement areas (one percent)

Land Cover

  • Dominant land cover is woodland (37 percent) and wetland (33 percent) followed by crop and pastureland (25 percent), settlement areas (three percent) and roads (two percent). From 2008 to 2014, there was an overall change of 42 hectares (from one land cover class to another) and is largely associated with crop and pastureland emerging as young woodland along with wetland encroaching into woodland. Another source of notable change is associated with the conversion of crop and pastureland to settlement
  • Woodland cover in the catchment has decreased by six hectares between 2008 and 2014 and interior forest habitat has decreased by 17 hectares
  • Wetland cover has decreased by one percent (76 ha) from pre-settlement times to the present and now occupies 33 percent of the catchment area

Other

  • There are approximately 170 to 180 in-use water wells with provincial records in this catchment. While most water wells are used for domestic water supply, in this catchment, several are used for commercial, industrial, agricultural or public water supplies
  • An Environmental Compliance Approval (ECA) has been issued for a renewable energy system in the vicinity of Gilroy Road and Donnelly Drive along the far eastern boundary of the catchment
  • Several PTTW have been issued in this catchment for an institutional water supply and dewatering at an aggregate operation
  • Part of a bedrock quarry license is located in this catchment and there are also three sand and gravel pit license in the catchment
  • An old landfill is located along the main river at the outlet of this catchment
  • Groundwater information from a discontinued historic Provincial Groundwater Monitoring Network PGMN well is available from the MOECC

Catchment Care

  • Twenty-one stewardship projects have been completed with assistance from the RVCA’s Rural Clean Water, Tree Planting and Shoreline Naturalization Programs (see Section 5 of this report for details)
  • Rideau Creek surface water quality has been monitored by the RVCA through its Baseline Monitoring Program since 2003. The surface water quality at site RCK-01 is monitored once a month from April to November
  • RVCA has been collecting benthic invertebrates in Rideau Creek at the Richardson Road site since 2003
  • RVCA conducted a fish survey along Rideau Creek in 2014
  • RVCA completed a the stream characterization survey on Rideau Creek in 2014, working upstream to the headwaters from the mouth of the creek where it empties into the Rideau River taking measurements and recording observations on instream habitat, bank stability, other attributes and preparing a temperature profile
  • RVCA completed 16 headwater drainage feature assessments at road crossings in the Rideau Creek catchment in 2014. This protocol measures zero and first order headwater drainage features and is a rapid assessment method characterizing the amount of water, sediment transport, and storage capacity within headwater drainage features
  • 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 Rideau Creek catchment
  • The Township of Montague has land use planning policies and zoning provisions - on water setbacks, frontage and naturalized shorelines and wetland protection - and in some instances use site plan control to implement these policies and provisions. Together with RVCA, the Township works with landowners on a case by case basis to enable new development while ensuring the scale is suitable on the lot, impacts on neighbours are minimized and development maximizes the watercourse setback
  • Development in and adjacent to the Provincially Significant Wetlands in the catchment (Pinery Road, Porter Swamp, South Montague Swamp) are 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