{"id":41543,"date":"2021-02-23T10:44:00","date_gmt":"2021-02-23T10:44:00","guid":{"rendered":"https:\/\/www.avizo.ca\/?p=41543"},"modified":"2026-09-29T14:22:36","modified_gmt":"2026-09-29T14:22:36","slug":"retention-ponds-stormwater-management-facilities","status":"publish","type":"post","link":"https:\/\/www.avizo.ca\/en\/2021\/02\/23\/retention-ponds-stormwater-management-facilities\/","title":{"rendered":"Retention Ponds: Widely Used Stormwater Management Facilities"},"content":{"rendered":"\n
This article looks at dry ponds and wet ponds (ponds with permanent storage). In addition to defining both types of ponds, we cover their advantages and disadvantages, design criteria and maintenance. Learn more about these popular stormwater management facilities.<\/p>\n\n\n\n
What is a retention pond?<\/h2>\n\n\n\n
Retention ponds are a type of stormwater management facility. They are designed to temporarily store stormwater before releasing it at a controlled rate into a watercourse. They are the most commonly used type of facility for managing stormwater in Quebec. They are generally built in low-density residential developments or in industrial or commercial areas.<\/p>\n\n\n\n
There are two types of retention ponds: dry ponds<\/strong> and wet ponds, also called ponds with permanent storage<\/strong>.<\/p>\n\n\n\n
What is a dry pond?<\/h3>\n\n\n\n
Dry ponds temporarily receive runoff during rainfall. They drain quickly (generally in less than 24 hours) and remain dry when there is no precipitation. Their main purpose is to reduce the amount of water in the storm sewer system during heavy rain to prevent downstream flooding.<\/p>\n\n\n\n
What is a wet pond?<\/h3>\n\n\n\n<\/figure>\n\n\n\n
Wet ponds, or ponds with permanent storage, hold a volume of water between rainfall events and have additional storage volume that varies with the flow. They provide water quality control in addition to quantity control. Pollutants are removed mainly by settling, but also through various biological processes.<\/p>\n\n\n\n
Advantages of retention ponds<\/h2>\n\n\n\n
Storing stormwater in retention ponds helps limit flooding and watercourse erosion. When well designed, they blend attractively into the urban landscape and can increase the value of neighbouring properties. They can also serve additional community functions, such as parks and playgrounds.<\/p>\n\n\n\n
Some advantages are specific to each type of pond:<\/p>\n\n\n\n
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Dry ponds stand out for their easy maintenance, good winter performance and low cost;<\/li>\n\n\n\n
Wet ponds remove various pollutants, whether in solid or dissolved form. They are more effective and require less space than constructed wetlands.<\/li>\n<\/ul>\n\n\n\n
Maintenance is needed less often than for other types of stormwater management facilities.<\/p>\n\n\n\n
Limitations of retention ponds<\/h2>\n\n\n\n
On the other hand, retention ponds:<\/p>\n\n\n\n
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require a large site, particularly wet ponds;<\/li>\n\n\n\n
require regular sediment removal to prevent resuspension;<\/li>\n\n\n\n
can lead to the accumulation of debris and the growth of weeds or odours. They therefore require regular maintenance to prevent outlet clogging and stagnant water;<\/li>\n\n\n\n
sometimes need a pretreatment structure to ensure satisfactory water quality.<\/li>\n<\/ul>\n\n\n\n
If poorly designed or maintained, wet ponds can:<\/p>\n\n\n\n
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create conditions that degrade water quality and lead to nutrients and metals entering watercourses. Proper management is therefore needed to prevent eutrophication in these ponds, as well as the proliferation of mosquitoes and frogs;<\/li>\n\n\n\n
discharge warm water in summer, which limits their use when fish species sensitive to thermal shock are present in the receiving watercourse.<\/li>\n<\/ul>\n\n\n\n
Wet ponds are also more expensive than dry ponds.<\/p>\n\n\n\n
![\"Diagram](\"https:\/\/www.avizo.ca\/wp-content\/uploads\/2021\/02\/bassin-de-retention-V2-1024x672.jpg\")
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