Bioretention cells, like the one pictured, are designed to capture stormwater runoff and infiltrate it into the ground. Plants use and evapotranspire some of the infiltrated water. In some designs, the infiltrated water moves deeper and recharges groundwater, while in other designs, a perforated underdrain at the bottom of the bioretention cell eventually delivers the water to the storm sewer system – ideally, after the storm has passed.
The picture above is one of the bioretention cells Anne and her collaborators studied in the project featured yesterday. This bioretention cell has an underdrain, so it probably wasn’t super-helpful at reducing total runoff volumes, but did delay water entering the storm sewer system and receiving stream.