Stormwater runoff flushes pollution into streams

Protecting our local waters


This is the first installment of Protecting Our Local Waters, a four-part series written by local government, education and nonprofit professionals in recognition of National Stormwater Awareness Month, observed each April.

The purpose of observing Stormwater Awareness Month is to provide general information to the public on the potential adverse impacts of stormwater runoff on the environment, to offer tips and information on how to reduce water pollution and to spread the word about local programs and ways to get involved protecting and restoring our creeks and rivers.

Stormwater runoff is the one of the largest remaining contributors of water quality degradation in the waterways of the United States. When land is converted from its natural state to one of parking lots, buildings, lawns, streets and sidewalks, rainwater that once soaked into the ground now flows over the hard, or impervious, surfaces and becomes stormwater runoff.

Unlike sewage, which is collected and treated at a wastewater treatment plant, anything that flows into a storm drain empties directly into the nearest stream or creek or into the ground, normally without any treatment.

Alterations to the natural, undisturbed environment cause impacts to the hydrologic cycle, both in terms of the quality of the water in creeks and rivers, and in terms of the quantity of fresh, cold water available during the summer.

Undisturbed land intercepts runoff and snowmelt, allowing water to slowly infiltrate and become available to vegetation, or to recharge groundwater. Only a small percentage or rainfall and snowmelt runs off undisturbed land.

Loss of native soils and vegetation generally occurs when land is developed, and the amount of rainfall and snowmelt running off the land as stormwater increases substantially.

This increased stormwater runoff transports pollutants such as oil, heavy metals, animal waste and sediment from construction sites, roads, highways, parking lots, pastures, lawns and other developed lands. These pollutants have harmed virtually all creeks, streams and rivers in Washington state in developed areas.

During the wet winter months, high stormwater flows can cause flooding, damage property and degrade wildlife habitat by eroding stream banks, widening stream channels, depositing excessive sediment and altering natural streams and wetlands.

In addition, impervious surfaces constructed during development mean less water soaks into the ground. As a result, drinking water supplies are not replenished and streams and wetlands are not recharged.

This can lead to water shortages for people and inadequate stream flows and wetland water levels for fish and other wildlife.

About one-third of Washington's waters are too polluted to meet state water quality standards. Locally, some of our creeks and rivers exceed water quality standards for fecal coliform, high temperatures, chlorinated pesticides and PCBs.

These local waterways also frequently do not contain enough dissolved oxygen; combined with high water temperatures, this can mean the creeks are no longer able to sustain fish.

High levels of fecal coliform can make fish, animals and people sick, and can even make swimming unsafe.

More than 60 percent of water pollution comes from things like cars leaking oil, fertilizers and pesticides from farms and gardens, failing septic tanks, pet waste and fuel spills from recreational boaters.

All these small, dispersed sources add up to a big pollution problem. But each of us can do small things to help clean up our waters too - and that adds up to a pollution solution!

Protecting Our Local Waters is a four-part series written by local government, education and nonprofit professionals in recognition of April being National Stormwater Awareness Month. For more information or ways you can protect our water resources, visit


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