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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 a designated Canadian Heritage River and an integral part of the Rideau Canal National Historic Site of Canada that is a UNESCO World Heritage Site and a major tourist attraction. Smiths Falls, Merrickville and Burritts Rapids are the main settlements in the subwatershed
  • The Village of Merrickville-Wolford is called the Jewel of the Rideau. It occupies the area of the catchment to the south of the Rideau River and is characterized by a diverse landscape. The largest centre of the community is Merrickville which is known for its boutiques and local craft people and artists. It is considered to be one of the best preserved 19th century villages in Ontario with more than 100 historic buildings designated. There are active farmlands, large wetlands, extensive woodlands, and cleared areas where full time farming has been abandoned because of marginal soil capability. The Rideau Canal National Historic Site of Canada has had a significant impact on the historic development of the Village, and continues to be an important influence on its role as an arts community which draws visitors from a large surrounding area as well as tourists visiting the National Capital Region. Within the Village, there are four lock stations, Edmunds, Kilmarnock, Merrickville, and Upper and Lower Nicholsons which provide places for public access to the Canal, passive recreation and presentation of the Canal story. The Easton-Kilmarnock marshes are among the most significant wetlands along the Canal, and the section of Canal from Merrickville to Burritts Rapids is a particularly scenic and historic area
  • 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 the Rideau-Merrickville catchment and the rest of the Middle Rideau subwatershed primarily resides within the Smith Falls Limestone Plain. This catchment is primarily underlain by Oxford Formation dolostone. The bedrock in the upper part of the catchment is mainly overlain by an array of glacial till, clay, and river deposits whereas most of the remainder of the catchment is overlain by a thin veneer of glacial sediment, referred to as ‘drift’ that is generally less than a metre in thickness. A geologic fault likely cuts through the northern western part of the catchment and the topography is generally flat
  • Fifty-three percent of the catchment lies within the Village of Merrickville-Wolford, 34 percent in the Township of Montague, seven percent in the Township of Elizabethtown-Kitley, three percent in the City of Ottawa, one percent in the Municipality of North Grenville, one percent in the Township of Rideau Lakes and one percent in the Town of Smiths Falls
  • Rideau-Merrickville catchment drainage area is 116 square kilometres and occupies about 14 percent of the Middle Rideau subwatershed and three percent of the Rideau Valley watershed

Vulnerable Areas

  • Lands along the Rideau River in the catchment are subject to flooding during the regional (100 year) storm. Flood elevations for this section of the Rideau River range from 104.4 metres above mean sea level (masl) downstream of the Edmonds Lock, to 103.7 masl below the Kilmarnock Lock, to 103.1 masl upriver of Mill Street in Merrickville, to 89.6 masl at the Andrewsville Bridge, to 89.2 masl upstream of the Burritts Rapids dam
  • The Assessment Report developed under the Ontario Clean Water Act identifies the upper bedrock aquifer underlying the majority of the catchment area as a Highly Vulnerable Aquifer, although, where sediments are thicker in a local area, the vulnerability would be less. The northern half of the catchment contains Wellhead Protection Areas A through D for the Merrickville municipal water supply; related provincial policies apply


  • Montague Township’s rural riverfront within the catchment along the north shore of the Rideau River includes a significant portion of wetland (locally and provincially significant) that takes up close to half of the overall shoreline frontage and as such much of the shoreline has retained its natural setting. The remainder of the frontage is primarily residential; however, with some exceptions mostly near Smiths Falls, the very dense small lot cottage development seen elsewhere in the subwatershed does not predominate here. Montague does not have a significant historical cottage pattern of development. Without the recreational waterfront component to the extent seen along the lakes, there is a less developed tourism infrastructure, although the river is part of the Rideau Canal corridor which attracts significant through boat traffic. While natural and environmental constraints would probably preclude a large scale obtrusive waterfront development project, there is likely opportunity for additional recreational development near the water in the Township. The wetland areas provide opportunities for low impact recreational activities such as fishing, hunting and bird watching. There is very limited amount, if any, public water access in Montague Township
  • Towards Merrickville, agricultural lands are more prevalent at the south end of Montague Township along the Rideau basin (with the best land from Smiths Falls to Kilmarnock along the Highway 43 corridor) and there is some residential estate development along the river with a mixture of historic stone houses and newer development during the last few decades. These tend to be on larger lots with increased waterbody setbacks. There have been a number of severances in these areas in recent years and shoreline protection has typically been a condition of development
  • Merrickville and Eastons Corners are the main settlements within the Village of Merrickville-Wolford portion of the catchment. Here, land use is predominately Rural and Agriculture with some areas of Wetland. A few private laneways with densely developed, undersized lots are found elsewhere along the Rideau River. Within the remainder of the catchment, land use is predominately Rural with some Natural Heritage-Provincially Significant Wetland designations

Conditions at a Glance

Water Quality

  • Surface chemistry water quality ratings in the Rideau River (Merrickville catchment) are “Fair” over two reporting periods (2003-2008 and 2009-2014)
  • Elevated nutrient and metal concentrations from inflows of nutrients (from private septic systems, agricultural and residential surface water runoff) are an occasional feature of the Rideau River. Surface chemistry water quality conditions have declined for both sites between the two monitoring periods. Decreased nutrient and metal concentrations are needed to improve the overall health of the creek

Instream and Riparian

  • In the Rideau-Merrickville catchment, the riparian buffer (30 m. wide strip along the shoreline of the Rideau River and its tributaries) is comprised of wetland (43 percent), crop and pastureland (26 percent), woodland (22 percent), settlement areas (six percent) and roads (three percent)

Land Cover

  • Dominant land cover is crop and pastureland (37 percent), followed by woodland (28 percent), wetland (19 percent), water (seven percent), settlement areas (six percent) and roads (three percent)
  • From 2008 to 2014, there was an overall change of 109 hectares (from one land cover class to another). Within the Rideau-Merrickville catchment, change is primarily associated with the transitioning of crop and pastureland to woodland and conversion to settlement along with the conversion of woodland to settlement and crop and pastureland
  • Woodland cover in the catchment has decreased by 20 hectares between 2008 and 2014 and interior forest habitat has increased by five hectares
  • Wetland cover has decreased by eight percent (900 ha) from pre-settlement times to the present and now occupies 19 percent of the catchment area


  • Approximately 720 to 760 in-use water wells with provincial records exist in this catchment. While most water wells are used for domestic water supply, several are also used for commercial, industrial, agricultural, municipal and public water supplies or monitoring
  • There are several Environmental Compliance Approvals in this catchment for discharge to the environment related to municipal and private sewage works; industrial and commercial air emissions and for waste management activities.
  • There are two sand and gravel pit licenses and an abandoned pit in the catchment
  • There are three Permits to Take Water TTW in this catchment for the municipal well water supply in Merrickville

Catchment Care

  • Seventy-four 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 River surface chemistry water quality is assessed by the Ministry of the Environment and Climate Change through its Provincial Water Quality Monitoring Program. The surface water quality sites at Andrewsville and Kilmarnock are monitored by the RVCA once a month from April to November
  • Well casings of the three drinking water production wells in Merrickville have been extended into the deep aquifer, resulting in a safer municipal drinking water supply
  • 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-Merrickville catchment
  • The Township of Montague, Village of Merrickville-Wolford and the Township of Elizabethtown-Kitley have 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, these municipalities work 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 (Barber’s Creek Marsh, Brassils Creek, Kilmarnock Marsh, Merrickville Marsh, Merrickville Wetland, Rideau River Part 1, Rideau River Part 4, Wolford Bog Complex) 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
  • The report entitled “A Multidisciplinary, Community-Based Study of the Environmental Health of the Rideau River” was prepared by the Canadian Museum of Nature in 2001. The study’s goals were to assess the biodiversity of the Rideau River, from Smiths Falls to Ottawa, and to reconcile local needs with long-term sustainable management of its biological diversity
  • Rideau Canal National Historic Site of Canada Management Plan (2005) update establishes the long term strategic direction for the management of the Rideau Canal and the Rideau Canal World Heritage Site Management Plan (2005) specifies how its world heritage values will be protected for present and future generations
  • The Landscape Character Assessment Report identifying key features and visual values along the Rideau Canal was released by the Rideau Corridor Landscape Strategy Steering Committee in April 2013 and includes recommendations for future planning and management actions to protect the visual setting of the Rideau Canal from Ottawa to Kingston, including those found in the Rideau-Smiths Falls catchment