What is a reservoir that temporarily stores storm runoff to reduce the runoff rate called?

The term for a reservoir that temporarily stores storm runoff to reduce the runoff rate is a detention pond. This type of facility is designed to manage stormwater by capturing runoff during rainfall events and releasing it at a controlled rate after the storm has passed. The primary purpose is to minimize flooding, reduce sediment transport, and improve water quality by allowing sediments and pollutants to settle before the water is discharged into natural waterways.

Retention basins, while similar, function differently as they are designed to hold water permanently and can contribute to groundwater recharge, whereas detention ponds serve a more temporary storage role. Other terms like holding tank may refer to storage for various other purposes, but do not specifically address the stormwater management function of slowing and controlling runoff flow. Stormwater basins can encompass a broader range of practices, but specifically describing the storage and release behavior characterizes a detention pond most accurately.