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What is Urban Stormwater?

When it rains or snows, where does all the water go? Does it soak into the ground? Does it sit in puddles until it evaporates? The water actually does both of these things. Some of the water will also flow over the land surface, heading downhill to the nearest stream or ditch. We call this stormwater runoff.

In cities and towns, the water can't soak through the pavement and rooftops like it can into the soil. As a result, cities have much more stormwater runoff than forests and fields do. The water flows off impervious surfaces such as driveways, rooftops, sidewalks, and parking lots, and then collects in gutters or basins which run directly into storm drains. These drains carry the water (as well as oil and other toxic chemicals caused by cars and households) directly to your local stream or lake.

Water quality in an area generally starts to become impaired when impervious land cover rises above 10%.  The more impervious cover, the greater the risk that your watershed is contaminated.

Don’t we live in a desert?  Why should I care about stormwater?

The Intermountain West has in recent years experienced some of the fastest urban growth in the United States.  With an increasing population comes an increased demand for water resources, particularly in watering lawns and gardens.  Water use in the West has grown so much that the Colorado River, a major water source, is completely used up before it even reaches the sea.

This rapid growth of development and water consumption are hard on the native desert ecosystems of our area.  These ecosystems are extremely delicate and take hundreds of years to develop.  As such, they suffer when humans impact them through construction.  Impervious surfaces such as roads and parking lots complicate the problem by introducing pollutants into the ecosystem.  During dry periods between rain events, pollutants build up on these surfaces.  The first storm after a long dry period then creates a “first flush,” sending that high concentration of pollution into the watershed.

Water in the West is a precious resource because we don’t have that much of it.  Climate change predictions for our area forecast fewer and more intense storms in the coming years.  That means water is becoming scarcer and we can’t afford to pollute it or waste it.  Through new management practices, we can reduce the impacts of impervious surface runoff and pollution.  We can also reduce the amount of rain water we waste by capturing it and using it on site.