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Retention pond photoRetention ponds

What are retention ponds?

Retention ponds, also known as stormwater retention basins or man-made lakes:

  • Store rainfall runoff from streets and adjacent lands
  • Are an efficient and cost-effective land drainage system, because fewer and smaller pipes can be used to carry runoff to the rivers
  • Benefit our environment by acting as a natural filter - they help to remove sediment and chemicals before the water drains to our rivers
  • Collect only land drainage, and not wastewater from homes or businesses
Is it normal for the water levels in the ponds to fluctuate?

Yes, particularly during spring and as a result of a heavy rain.

How does water get into the retention ponds?
  • The water, called runoff, flows down the street and drains into catch basins or storm drains (you might recognize them as grates along the curbs of the roads).
  • Some catch basins direct the runoff to pipes that drain into retention ponds.
How do the retention ponds act as a natural filter?
  • Sediment in the runoff settles down in the calm waters of the retention pond, and chemicals, such as lawn fertilizers, are consumed by naturally occurring aquatic vegetation.
  • As a result of natural processes, cleaner water slowly drains from the retention ponds into the rivers.
OKCan I use the water from the retention ponds?

No, you must not use the water from the ponds for any purpose. The water, or runoff, that flows into the retention ponds:

  • Contains pollutants that drain from:
    • the street (e.g., gasoline, oils, antifreeze, street salts)
    • neighbouring lawns and gardens (e.g., animal waste, geese droppings, herbicides, fertilizers)
  • Sometimes contains a type of naturally occurring algae that can irritate your skin and cause illness if swallowed

For your safety and the safety of your pets:

  • Do not use the ponds for any recreation activities where your body is in contact with the water (e.g., swimming, windsurfing, waterskiing)
  • Do not allow your pets to drink or swim in the water
  • Do not water your lawn with water from the ponds
  • Do not eat the fish
OKCattail photoCan I use the retention ponds for winter recreation activities?

No. Retention ponds are not safe to use for winter recreation activities because ice conditions can change quickly and without warning, creating an extreme, hidden hazard. During the winter, water from early snowmelt or nearby water main breaks drains into the retention ponds. This winter runoff is often mixed with street salts that can cause the ice to melt and thin quickly. The water enters the pond  underneath the ice, resulting in a thinning of the ice that can't be seen from the surface.

OKCan I use the retention ponds for boating?

Yes, but only boats without a motor (e.g., kayaks, canoes, pedal boats).

How do fish get in the retention ponds?

Fish can get into the ponds by swimming upstream from the river when water levels are high.

Do you maintain the retention ponds?

Yes, we:

  • Maintain and operate valves, fountains, and underground structures in the ponds (such as pumps, wells, and gates)
  • Maintain park areas near the ponds
  • Pick up debris periodically from the pond and surrounding public property
  • Control the grasses and weeds that grow through the stone shoreline
  • Treat aquatic vegetation (algae and water weeds) if necessary
Do you treat aquatic vegetation?

Yes, we have a program to maintain a healthy level of vegetation in all ponds except for naturalized ponds (e.g., Royalwood, Sage Creek). Depending on the depth of the pond, we use a harvester to cut out the vegetation and/or apply chemical herbicides approved by Manitoba Conservation and Water Stewardship. We are evaluating environmentally friendly methods of vegetation control that we expect will replace chemicals in a few years.

A large paddlewheel driven barge, or harvester, cuts and physically removes the vegetation from the ponds. Since the harvester can work only in water more than two feet deep, it can't remove vegetation along the shoreline.

A licensed contractor applies chemical herbicides to the water surface of those small or irregularly shaped ponds where the harvesting method is not practical. The contractor also applies an herbicide to the stone edging along the shoreline on public property to treat grasses and weeds.
Cattail photoDo you remove bulrushes or cattails from the shoreline on private or public property?

No. We do not maintain shorelines or landscaping on private property. Some people are in favour of this vegetation because it gives the retention ponds a more natural appearance. Also, bulrushes and cattails are an essential part of the wetland habitat, and provide food and shelter for ducks, waterfowl and other wetland creatures. However, other people prefer a more groomed appearance, so residents may maintain the shoreline behind their homes as they choose, except for residents living on naturalized ponds (e.g., Royalwood, Sage Creek).

Why do the retention ponds sometimes smell or look thick and clumpy in the spring and summer?

Retention ponds are like marshes. In the spring, a 'rotten egg' smell can occur because the snowmelt gets into the ponds and mixes with stagnant water. In the summer, slow-draining bodies of water smell of the fish, animals and plants (especially algae) that live in the water.

Algae may also smell, especially in summer during an 'algae bloom', when they grow in abundance. During an algae bloom, the algae appear as a floating green layer on the retention ponds. It sometimes resembles thick pea soup or paint.

For more information on algal blooms, please read the Manitoba Government's fact sheets or visit

Is there anything I can do to reduce algae and weeds?

Yes. Use less lawn fertilizer and pick up dog waste. These materials contain nitrogen and phosphorus, which are nutrients for algae and weeds. Reducing the amount of nutrients helps reduce the amount of algae and weeds.

According to a new provincial regulation, you must not apply fertilizer (not even zero phosphorus fertilizer) within three metres (10 feet) of the pond.

What is purple loosestrife?

A perennial herb, purple loosestrife is a noxious weed that grows nearly two metres tall. In mid-summer, this weed has vibrant purple flowers. Purple loosestrife invades and destroys wetland communities, such as retention ponds, by choking out native vegetation. Help keep Winnipeg free of this invader by removing and disposing of the weed.

How can I keep the geese from my lawn?

Information on techniques to make your lawn less attractive to geese is available at:

Are you doing anything to address the large geese population in our city?

Yes, we are working on stategies to manage Canada geese around retention ponds, roadways, and other locations in our city. For more information, visit

For more information on how you can be involved, visit Canada Goose Citizens' Information Network


Contact 311

Last updated: October 8, 2021

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