How Do We Treat Rainwater Runoff as a Resource?

Stormwater facilities at the Saint Paul Port Authority’s Beacon Bluff Business Center treat rainwater as a resource that is used to recharge groundwater, irrigate landscaping, as well as enhance and protect our natural environment.  Approaches to stormwater and runoff treatment are represented by the three states featured below; pursuing the Restorative State is the most ecologically responsible management solution to this challenge in an urban environment.

THE NATURAL STATE

Pre-Development

Water reaches the earth’s surface via precipitation (rainfall, snow, etc.).  The combination of water given off by plants and water that evaporates is called evapotranspiration.  In the natural environment, almost half of this water is either absorbed by plants or evaporates back into the atmosphere as water vapor.  Roughly 50% of the precipitation infiltrates into the soil, helping to recharge groundwater resources. Typically 10% runs over the surface and is filtered by forests, grasslands and wetlands before entering our lakes and rivers.

THE RESTORATIVE STATE

Working With Nature

Next Generation Stormwater Management is defined by rainwater and runoff treatment solutions that mimic natural abilities to reduce stormwater runoff, reduce downstream pollution, and utilize rainwater as a resource for groundwater re-charging, irrigation, and enhancement of our rivers and lakes. Human health and commerce depend on the earth’s natural ecosystems for purified air, pollination, aquifer recharge, erosion prevention, climate stability, and more; there is an interrelationship between the development of humans and nature.  Our natural resources must be treated with care and responsibility.

The stormwater demonstration area in front of you depicts how nature and humans manage stormwater.  The small amount of water used in this demonstration is being collected in an underground cistern.  That water is then used to irrigate the grass and other plants in this public plaza.

THE URBAN STATE

Working Against Nature

In a highly-developed urban environment, soft vegetated ground is replaced by hard (impervious) surfaces consisting of pavements, building, rooftops, etc.  In this state, as much as 95% of rainwater is untreated and becomes potentially polluted runoff. Water flowing over hard surfaces collects sediments and pollutants.  Traditional curb and gutter drainage systems are designed to quickly move stormwater away from streets and sidewalks, which means sediment and pollutants are transported directly into rivers and lakes. In addition, downstream flooding is increased as rainwater that was previously naturally attenuated is rapidly moved downstream.