||It has been suggested that Stormwater management pond be merged into this article. (Discuss) Proposed since February 2013.|
A retention basin is used to manage stormwater runoff to prevent flooding and downstream erosion, and improve water quality in an adjacent river, stream, lake or bay. Sometimes called a wet pond or wet detention basin, it is an artificial lake with vegetation around the perimeter, and includes a permanent pool of water in its design.
It is distinguished from a detention basin, sometimes called a "dry pond," which temporarily stores water after a storm, but eventually empties out at a controlled rate to a downstream water body. It also differs from an infiltration basin which is designed to direct stormwater to groundwater through permeable soils.
Wet ponds are frequently used for water quality improvement, groundwater recharge, flood protection, aesthetic improvement or any combination of these. Sometimes they act as a replacement for the natural absorption of a forest or other natural process that was lost when an area is developed. As such, these structures are designed to blend into neighborhoods and viewed as an amenity.
Design features 
Storm water is typically channeled to a retention basin through a system of street and/or parking lot storm drains, and a network of drain channels or underground pipes. The basins are designed to allow relatively large flows of water to enter, but discharges to receiving waters are limited by outlet structures that function only during very large storm events.
Retention ponds are often landscaped with a variety of grasses, shrubs and/or wetland plants to provide bank stability and aesthetic benefits. Vegetation also provides water quality benefits by removing soluble nutrients through uptake. In some areas the ponds can attract nuisance types of wildlife like ducks or Canada Geese, particularly where there is minimal landscaping and grasses are mowed. This reduces the ability of foxes, coyotes and other predators to approach their prey unseen. Such predators tend to hide in the cattails and other tall, thick grass surrounding natural water features.
See also 
- Nationwide Urban Runoff Program (NURP) – US stormwater research project
- Settling basin – for treating agricultural & industrial wastewater
- Stream restoration
- Sustainable urban drainage systems
- Urban runoff
- Water pollution
- Sustainable Flood Retention Basin
- Balancing lake (UK)
Other meanings 
A retention basin can also be a part of a nuclear reactor used to contain a core meltdown.
- Water Environment Federation, Alexandria, VA; and American Society of Civil Engineers, Reston, VA. "Urban Runoff Quality Management." WEF Manual of Practice No. 23; ASCE Manual and Report on Engineering Practice No. 87. 1998. ISBN 1-57278-039-8. Chapter 5.
- U.S. Environmental Protection Agency. Washington, D.C. "Preliminary Data Summary of Urban Storm Water Best Management Practices." Chapter 5. August 1999. Document No. EPA-821-R-99-012.
- Mississippi State University. College of Engineering. Stormwater Retention Basins. Chapter 4, Best Management Practices.
- Urban Drainage & Flood Control District, Denver, CO. Urban Storm Drainage Criteria Manual. Volume 3, Structural BMPs.
- Virginia retention basin standards
- Detention vs. retention – Harris County, Texas Flood Control District
- Stormwater Ecological Enhancement Project – University of Florida
- The use of retention ponds in residential settings
- International Stormwater BMP Database – Performance Data on Urban Stormwater BMPs