by Brian Lavendel
Pollution of lakes, rivers, streams, oceans: it’s a problem many of us are aware of and concerned about. The good news is that today, the actions of individuals can have a large impact on the quality of our waters. Yes, each one of us can help keep our water clean. The key phrase is “non-point source pollution.”
Many of us still think that water pollution originates from large pipes protruding from factories and extending out into a nearby pond, stream, river, or lake. Years ago, this image of water pollution was accurate. Sewage, wastes, and polluted water often flowed directly from such pipes into surface waters. This type of pollution is known as “source point” pollution, by virtue of the fact that it comes from a localized and clearly identifiable source. Decades ago, such scenes were not uncommon. Today, however, thanks in large part to legislation, regulation, and public pressure, most source points have been sharply reduced or eliminated. Today, the water that comes from factories or sewage treatment plants must meet stringent standards for pollutant levels, and violators of those standards are subject to stiff fines. No longer, then, is local industry the main source of surface water pollution. Instead, the major source of today’s water pollution is much more widespread and less site-specific. Thus it is termed non-point source pollution. Where does non-point source pollution come from? From me and you.
One way to understand why non-point source pollution is a problem is to realize that normal, everyday human activities have a significant impact on the water quality of lakes, streams, and rivers. Bodies of water do change over time even in the absence of human activity. Gradually, streams fill with sediment, rivers change course, and lakes eutrophy (or age) over time. But, as is true of human interaction with the environment in so many ways, our activity has greatly accelerated these natural processes, so that it threatens the viability of aquatic life and the future of water quality.
It stands to reason, however, that if we humans are such contributors to surface water pollution, we might also be able to alleviate much of the damage by changing our activity.
To understand how surface waters are polluted, we need to look at what seems to be a harmless part of nature: the raindrop. Usually it’s not the raindrops themselves that pollute the water (although some contaminants are carried from the sky via raindrops–acid rain is one example), but what the raindrops pick up as they move toward surface waters. When much of our landscape was undisturbed by human development–both rural and urban, most rain would fall on vegetation, or on forest or prairie floors which were covered with organic matter and had deep and stable soil. Generally speaking, then, this rain (now “run-off”) would be soaked up by the vegetation, organic matter, and soil, or–at the very least–filtered and slowed in its movement.
Let’s fast forward to present time, when agriculture and urban development cover a large portion of our globe. Now, rainwater lands on a much altered surface. In rural areas, of course, much of the native vegetation has been cleared for agricultural development. Most conventional farming today involves extensive tilling of soil and the use of heavy machinery over large areas in the production of monocultural, annual row crops, which often leaves soil exposed. Picture that rain drop again, and see it fall on to bare soil with an impact capable of disturbing, picking up, and quickly carrying away particles of soil (since there is no vegetation to slow it down or filter it along the way) to the nearest ditch or gully, where it joins other raindrops also carrying soil, rushing forth to the nearest body of water. (To make matters worse, these drops of water falling over agricultural areas also pick up fertilizer, pesticides, herbicides, fungicides, and animal manure–all of which end up polluting surface waters.)
But one can’t blame non-point source pollution on farmers alone. In recent decades, farmers have learned a great deal about managing manure, keeping cattle out of streambeds, conserving soil, and generally reducing or filtering run-off in recent decades. The U.S. Soil Conservation Service sees to it that for farmers to be eligible for government programs, they must file soil conservation plans. But the best reason for farmers to protect their soil is that without it, they would eventually be out of business. Fertile, productive farms need good soil. So farmers have learned that when they contour strips for crops, or puts grass buffers between fields, it’s not only good for the environment, it’s good for the crops.
Today, according to the University of Wisconsin Extension, agricultural run-off actually carries less sediment (per acre) into surface waters than urban areas. To understand this, let’s go back to the raindrop. This time, picture it falling in an area of urban development. Where, before, the raindrop fell on thick native vegetation, it now falls on rooftops, lawns, driveways, parking lots, and highways. And once again we have the same problem–little opportunity for that raindrop to be absorbed, filtered, or slowed by vegetation. Instead, it goes rushing (probably faster than that raindrop out in the country) across pavement, into the gutters, down storm sewers, and into the stormwater system, before finally flowing into a lake, stream, or river. (Although many people think that the water which runs down the gutters is sent to a sewage treatment center, that is very rarely the case. Most often, the water you see rushing down the storm sewer–and all the pollution it picks up along the way–goes straight into the nearest surface water without any cleaning or “treatment.”) The vast majority of surfaces in our urban areas, which were covered previously by vegetation and thick, porous soil, are now impervious to water. Thus those paved areas compound the problem: not only are there more contaminants to pollute the water, but at the same time there is less porous area to absorb, filter, or slow it down.
What does this urban raindrop carry into the surface waters? A study conducted for the Wisconsin Department of Natural Resources found significant amounts of sediment, nutrients, metals, pesticides, and other chemicals. Where do these pollutants come from? From you and me–from everyday human activity. Let’s start at home. If you live in a typical suburban house, your home is one source of run-off. The gutters and downspouts that collect the rainfall from your roof are major sources of run-off. This water, which is typically flowing quickly and concentrated into a small area, picks up loose soil particles, grass clippings, leaves, pet waste, fertilizer, pesticides, herbicides, and whatever else may be on your lawn, sidewalk, or driveway.
What does this mean for the surface water in your area? The soil particles (or sediment) cloud the water, cover fish spawning areas, and fill in waterways and bodies of water, causing the temperature of the water to rise. Grass clippings, leaves, pet waste, and other organic matter are swept into the water where they begin to decay and to provide food for bacteria and algae, which multiply, blocking light for bottom plants.
The bacteria then use up oxygen (which is essential for fish), and their decay produces ammonia which can poison fish and other aquatic life. The fertilizers (many of which contain pesticides and herbicides) feed algae and weed growth, further contributing to the process described above. Pesticide and herbicide poisons often find their way into the fish and the birds which feed on those fish, where they build up over time. Overall, the effect is cumulative, giving rise to significant contamination and degradation.
Of course, the water pollution that results from any one home is relatively minor, but, added up, residential homes, lawns, and paved areas are major contributors to surface water pollution. If we avoid the attitude which is embodied in phrases such as “What difference can one pile of leaves or one application of fertilizer and weed-killer make?” we will discover that one person can in fact make a difference. The automobile is another significant contributor to non-point source pollution. Not only does the automobile itself yield dangerous pollutants, but roads and highways act as highly efficient pathways to carry those pollutants directly into our surface waters. Have you ever seen streets swollen with the rain water of a powerful summer storm? Those rivers of water flow down the storm sewer system to–you guessed it–surface waters. And they pick up the waste particles from automobiles along the way. (Moreover, it doesn’t take a huge downpour to pick up and move these water contaminants–even a small shower will do it, it’s just harder for us to see.)
Perhaps you’re surprised to learn that your car or truck contributes to water pollution. Nevertheless, your vehicle leaves behind chemicals such as lead, zinc, cadmium, and chromium, in the form of paint pieces, metal pieces, exhaust solids, as well as leaked coolant, oil, windshield washer and other fluids. Once again it’s a matter of numbers. One car alone won’t pollute a river, but tens of thousands will and do.
In addition to the waste that comes directly from the automobile, streets and highways contribute to water pollution in other ways. Do you live in an area where snow and ice affect winter driving? If so, chances are that salt and sand are used on those roadways. Guess where it all goes when the snow melts? And all the litter–from cigarette butts to empty soda cans–goes with it.
Where else does non-point source pollution come from? There are numerous other sources, too many to mention here. But a very significant source is construction. In the construction of a new road, house, or industrial park, soil is exposed, disturbed, and often moved in large quantities. As you know, such exposed soil is extremely subject to erosion. Studies of areas under development have shown that more than two dump -truck loads of soil can be washed away from one acre of development. Today, developers are required to employ practices which reduce the soil run-off by placing silt barriers such as fabric or straw bales around the perimeter of the area.
Reducing non-point source pollution does require the investment of effort and money (although a great deal of contamination can be avoided merely by changing our practices). But the cost of not taking action is even higher. Consider the use we (and the other life that shares our planet) make of our surface water resources. Recreation is an obvious example. We use our lakes, streams, and rivers for fishing, swimming, and boating. And often, we visit bodies of water for the aesthetic pleasure afforded by moving water–the sound and smell of ocean surf, or the sight of moonlight reflected in the waters of a lake.
We also use surface waters for our sustenance. Cities such as Milwaukee or Chicago, for example, obtain their drinking water from Lake Michigan. Much of the western U.S. obtains water from dammed rivers and man-made reservoirs. And even though municipal water is often cleaned and filtered, such processes are expensive and less than one hundred- percent effective. If that were not reason enough to be concerned about non-point pollution, there is some evidence that below-ground sources of water are also subject to contamination from non-point sources.
Perhaps the most profound reason for reducing water pollution is that, since it is the source of so much of environmental degradation, we must take responsibility for cleaning up our own mess. If we are indeed stewards or caretakers of the land (and water), we must see to it that the impact of our actions is minimized. This obligation extends not only to our co-habitants in the planet and to the animal kingdoms, but to future generations of humans. Fortunately, non-point source pollution is one aspect of human impact which we can reduce.