Detention ponds and retention ponds are both used to manage stormwater, but they serve different purposes. While the terms are sometimes used interchangeably, understanding the difference is important when discussing drainage, stormwater management, and post-construction site design.
What Is a Detention Pond?
A detention pond is designed to temporarily hold stormwater and release it at a controlled rate.
During a storm event, runoff enters the pond and is temporarily stored. Water is then gradually released through an outlet structure, helping reduce peak flows and manage the amount of runoff moving downstream.
A detention pond may be dry or have limited standing water between storm events, depending on its design and local conditions.
Detention ponds are commonly used in developments, commercial properties, and other areas where increased impervious surfaces have changed natural drainage patterns.
What Is a Retention Pond?
A retention pond is designed to hold water more permanently.
Unlike a typical detention pond, a retention pond generally maintains a permanent pool of water. Stormwater enters the pond and is stored, with water leaving through evaporation, infiltration, or a controlled outlet depending on the design.
Retention ponds can provide stormwater treatment and may also offer additional benefits such as habitat or aesthetic features.
The Simple Difference
The easiest way to remember the distinction is:
Detention = temporarily holds and releases water.
Retention = retains water and typically maintains a permanent pool.
Both types of ponds can play an important role in managing stormwater, but the appropriate design depends on the site’s drainage characteristics, soil conditions, regulatory requirements, and project goals.
Why Does This Matter?
Stormwater ponds can require ongoing inspection and maintenance after construction. Sediment accumulation, erosion, vegetation, damaged outlet structures, and other issues can affect how effectively a pond functions.
For permanent stormwater facilities, understanding whether a site has a detention pond, retention pond, or another type of stormwater facility is important when developing inspection and maintenance procedures. Post-construction, these inspections are typically conducted annually.
In Colorado, local requirements may also determine how permanent stormwater facilities are designed, inspected, and maintained.
Final Thoughts
Detention and retention ponds both help manage stormwater, but they do it differently. Detention ponds are primarily designed to temporarily store and control the release of runoff, while retention ponds generally maintain a permanent pool of water.
Understanding the difference can help property owners, contractors, and project teams better understand the purpose and maintenance needs of these important stormwater facilities.
At Summit Services Group, we provide stormwater inspections and compliance support for construction and permanent stormwater facilities across Colorado.