It’s time to play Follow the Water. Take advantage of the next time a heavy rainstorm occurs on your schoolyard. Put on your rubber boots, go outside, and pay attention to what happens to the water as it lands on asphalt and cement. Follow it as it moves downhill toward a storm sewer and grab a sample of it just before it dives in. How clean does it look and smell?
Next follow the water as it moves downhill toward a garden or even a mowed yard. What happens to it there? Most likely, unless it’s a major downpour or a rain that has lasted for hours, the water is soaking into the soil.
Soils and vegetation work together to absorb water. An ecosystem has ways to keep resources onsite, including water and nutrients. These ways include slowing water down using vegetation, porous soils, downed logs, beaver dams, ground squirrel holes, and other structures. When water slows down, it has a chance to drop its sediment load and to enter soils where it moves deeper, going through a filtering process that removes nutrients and contaminants. The water is available for plants, rather than running down some pipe to a reservoir, river, lake, or ocean.
This is the idea behind an increasing emphasis on mimicking natural processes for managing stormwater in cities. There’s an excellent article in Yale Environment360, To Tackle Runoff, Cities Turn to Green Initiatives, that mentions some of these new techniques, and provides some surprising statistics about stormwater runoff. Some of these features would be easy projects for schoolyard habitats, providing valuable ecosystem services like filtering water and preventing erosion, while providing habitat for insects, spiders, plants, birds, and numerous other organisms.