Monday, November 8, 2010

Muddy Water Watch

Can you name the most common water pollutant? You might think pesticides, animal manure, or industrial chemicals. Nope. The most common water pollutant is plain old dirt. Take a look at your local creek or river the next time it rains, and note whether or note the water is still fairly clear, or looks like the color of mud. I know in my state, creeks look like liquid red clay after every major rain storm. I usually have an urge after a heavy rain to collect some water and see what the mud to water ratio really is.

Why is dirt harmful? I mean, it's a natural substance, and dirt gets into streams and creeks no matter what we do. That's true. The problem is when excessive amounts of dirt, also called sedimentation, washes into streams. It chokes plant and animal life, and can even cause problems for water treatment plants.

One of the last times I kayaked a major rivers in my area, the water was so red and soupy that I couldn't see more than an inch under the surface. Usually I don't want to fall out of my boat because I worry about water snakes. That day, I didn't want to fall out of my boat because it looked like quicksand. I had visions of the muddy water sucking me down into the depths. My friends would never find any trace of me, just a lonely kayak aimlessly floating down the river. I decided to put on my life jacket pretty soon after getting on the river.

Sedimentation causes problems for native fish and other animals by ruining their habitat. Many types of fish  live and lay eggs around loose gravel or cobblestones littering the bottom of streambeds. Sedimentation will fill in all of the gaps between small rocks, eliminating good fish habitat. Dirt can infiltrate fish gills, making them suffocate. Sedimentation also ruins habitat for other types of aquatic animals, like invertebrates that burrow underneath rocks. All of that dirt and silt will smother any kinds of plants growing in the stream. Plants are often either hiding places for fish, or food for a variety of animals. Sediment in the water is no good for any type of creature or plant that calls the water home.

Sedimentation is also expensive for people. It mucks up water treatment facilities, increasing the cost of cleaning up our drinking water by up to 60%. Excess dirt in the water also means other nasty things have been washed in too. Usually, sediment can carry pollutants that we typically think are main water pollutants: oil, grease, fertilizers. When dirt runs into the creeks, everything sprayed on or in contact with the dirt washes in too.

Polluted runoff from construction sites sends about 80
million tons of sediment into the nation's water bodies
each year. Credit: Waterkeeper Alliance
So how does all of the dirt get into the water? There are a couple ways. In my area, farmers sometimes till up their fields right up to the edge of a creek. That means when it rains, the water runs through the fields, picks up all that loose dirt, then flows right into the creek. Luckily many new initiatives are educating farmers about the benefits of leaving a buffer zone between fields and any water body. The most common way dirt gets into water is from housing developments. In these cases, developers bulldoze land right to the edge of a river, causing lots of problems even after the new homes are completed. If ground cover is removed right to the river's edge, there is nothing to hold back the dirt. Sometimes it can be hard to get grass or other ground covers to grow back right next to an active stream. But developments don't even need to be right next to a river to cause big problems. Developers like the one shown in the above photo make tons of dirt wash into storm drains. All that mud then flows straight into the nearest creek.

Regulations are supposed to prevent this kind of development, but in my state many developers either aren't aware of the laws, or just ignore them. Luckily, there are several new programs in the works to educate the development community and to report construction sites that aren't doing enough to stop dirt from flowing into our waterways. Muddy Water Watch started in North Carolina, and was so successful that Alabama has started its own program. The program educates developers about the real truth of effectively controlling sedimentation: it's cheaper for them. Yes, that's right, keeping sediment under control actually decreases long-term construction costs. But few developers seem to know that.

Check out the Muddy Water Watch site, and read up about sedimentation. If it's a problem in your area, find a local river conservation group and see if you can get involved in educating the public and the development community about the damage sediment does to our rivers and to our economies.

1 comment:

0s0-Pa said...

Very interesting post on the harmful contaminants that stem from a lack of proper sediment control. I never would have guessed that dirt was the most harmful stormwater pollutant.