Ask A Scientist© Environmental Earth Science Archive

name         Dave L.
status       other
age          30s

Question -   What is the difference between a water retention pond and a water detention pond?  I have 
heard of a water retention pond but never a water detention pond.  Is there such a thing as a water 
detention pond?
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A retention pond is designed to hold a specific amount of water indefinitely.  Usually the pond is 
designed to have drainage leading to another location when the water level gets above the pond capacity, 
but still maintains a certain capacity.

A detention pond is a low lying area that is designed to temporarily hold a set amount of water while 
slowly draining to another location.  They are more or less around for flood control when large amounts 
of rain could cause flash flooding if not dealt with properly.  For example, in my housing plat, we have 
a detention pond that all of the drainage from our streets run into.  Normally it is a grassy field with 
a couple of concrete culverts running towards a drainage pipe.  During the last couple of weeks with all 
the rain here in Ohio, all of our street drainage has run off into this area and filled it to near capacity 
last week.  As of today, you can see the water level nearly gone due to the planned drainage and 
evaporation.

Hope this helped explain things.

Regards,

Chris Murphy
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A water detention pond, by definition, detains water.  When an area is paved, or covered with a building, 
water runs off the property much faster than when it is in a natural state.  The total amount of discharge 
is the same, but the discharge happens over a shorter amount of time.  A hydrologist will design a water 
detention pond to temporarily detain the water and keep the runoff to the desired rate.  When the rain 
ends, though, the water detention pond will be empty shortly afterwards.

A water retention pond, on the other hand, retains water all the time.  The pond level may go up and down, 
but ordinarily the pond has some water in it. So, if the pond is typically empty except during and shortly 
after rain or other precipitation, it is a detention pond.  If the pond always has water in it, then it is 
a retention pond.

Andy Johnson
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