Water is a necessity for life. We use it daily to drink, bathe, wash our clothes, clean our dishes, water our yards, and wash our cars. A good deal of the water that we use every day comes from lakes and reservoirs. And much of our nation's water supply is polluted. How did it get that way?
When it rains or snow, fresh water falls from the sky to the earth. This water hits the earth's surface, becomes runoff, and ends up in our lakes, rivers, reservoirs, and streams. The fluid in these water bodies is then evaporated into the air to form clouds, which then form rain and snow again. This is called hydrologic cycle and it is a constant process on earth. It's also one of three sources of pollution of lakes.
When water evaporates in the air above a coal burning energy plant, the water droplets pick up pollution particles. Polluted water droplets then fall to the earth as rain or snow, thus polluting everything the drops touch, whether it be the surface of a lake, your front yard, or the street. In areas of our country that have a high volume of factories pumping pollution into the sky, the affect is devastating. Imagine every raindrop containing pollutants dropping on the surface of a lake? That's a lot of pollutants being absorbed into a carefully balanced ecosystem. Not a pretty picture.
The Great Lakes hold one-fifth of the earth's surface fresh water supply. These lakes are notoriously polluted. In addition to being polluted from the air, the Great Lakes are also polluted from runoff. Runoff is the middle step of the hydrologic process in which rain and snow melt, picking up pollution in the form of fertilizer and pesticides. Runoff then washes down our gutters, culverts, and ditches right back into the water supply. Let's throw in some road salt, oil from cars (most roadways have drainage to prevent flooding), and an abundance of human and animal waste. It's a nightmare cocktail being dumped into our lakes on a regular basis.
Wait! There's one more way to pollute a lake. It's pretty safe to say that sewage and industrial waste needs to go somewhere. We all create it. But what do we do with it? In the Great Lakes, there are huge sewage pipes that run into the lakes. At the open end, "clean" sewage is pumped right into the lake. The pipes are called effluent out falls. And while they are a necessity, regulating what is released from these out falls is a major concern. Human and toxic metals regularly make their way right into our lakes. Yes, that's what's in our water supply.
But it used to be so much worse. In the 18th and 19th centuries, everything was dumped right into our waterways because people believed that water could dilute anything. Waste, industrial pollutants, fertilizers, pesticides, heavy metals, and just about everything else went right into the water. Wait, there's a little bit more. Sometimes, factories dumped heated waste into the lakes, thus causing changes in the water temperature. So on top of the waste problem, algae blooms and fish kills were abundant. At the time, no one realized the long-term impact on the ecology of a water body or how long it takes from a lake to recover from such extreme pollution.
So what happens when all this pollution hits our lakes? Just like when throwing a handful of sand into the ocean, polluted sediment settles to the lake bottom. Water droplets containing particles of pollution blend with the surface water, releasing their fine grains of pollution. These settle too and the effect on a lake is devastating. Fish die, grasses run rampant and smother the oxygen supply, and algae blooms out of control. Thus, lakes fall out of balance with nature. This is why we definite pollution as a change in the chemical, physical and biological health of waterway due to human interaction.
Awareness and control of the pollutants that affect our water supply is the only thing that will bring about change in our lakes. We cannot continue to harm the plants and animals that live in these delicately balanced ecosystems. We all need to be concerned that pollutants affect every single thing that uses a lake; from the microorganisms on up to the humans.