Water pollution not always obvious

The words “water pollution” often conjure up an image of waterways thick with sludge and stinking of sewage, with trash and tires, and maybe dead fish floating belly-up on the surface. When we think of the culprits, we may picture a big industrial plant, spewing toxic chemicals into a nearby river.

However, water pollution takes another form that is harder to identify and fix.

It is called non-point source pollution because there is no single pipe, or source, we can point to as the culprit. Non-point source pollutants are often useful substances that have escaped from their proper place into our waterways. A good example is plain old soil.

Soil is great on forest floors, farm fields and yards. But in creeks and streams, too much soil causes havoc. Loose soil in the water is called sediment, and it piles up on the streambed, filling in deep pools and burying rocks and gravel. Those deep pools and rocky areas are exactly what aquatic critters need to live. These areas make up their habitat.

Rocky areas cause the water to form ripples, and ripples gather oxygen from the air. Aquatic insects cling to those rocks and live there, in turn providing food for fish. When sediment buries the rocks, it smothers the insects and smooths out the flow of the water so that it gathers less oxygen. With less oxygen in the water, bugs and fish die out.

Deep pools tend to be colder than shallow water, and many kinds of fish, especially trout, require cold water to survive. As sediment fills in deep pools, trout and other fish lose their cool refuges and die out. Also, cold water holds more oxygen than warm water, so the shallowing of streams reduces their total oxygen-holding capacity.

Where does all this sediment in the water come from?

It is a non-point source pollutant – it comes from all over the surrounding land, carried by rainwater. Unpaved roads, recently tilled fields and construction sites are primary sources of sediment that washes off the land and into creeks and streams. Each little input of loose soil isn't so bad by itself, but the cumulative effect is devastating to the health of our streams.

Everyone's help is needed to stop the run-off and erosion that contributes to sedimentation. Look for run-off and erosion on your property and throughout the community: Notice unpaved roads very close to a creek or stream, with little or no woody vegetation in between. Notice drainage ditches or creeks next to fields, with little or no woody vegetation on the banks to catch soil. Notice landscaping or construction projects with lots of bare soil and no fencing to contain it.

If you see an area that could be contributing to sediment in a creek or stream, contact N.C. Cooperative Extension. We can work with you to fix the problem, and we may even be able to find funding sources to help pay for the work.