Well, there's good news and bad news. The bad news is there is a limited amount of water on earth. In fact, there's no more water today than there was when the earth was formed. The good news is water is recycled. Over time, it's used over and over again. Because of this, it's very important not to pollute water so that it can be used again safely by humans, fish, and other life forms that depend on it.
The heat from the sun causes water on the earth to evaporate, or turn into a vapor, and rise into the air. As this vapor rises, it cools, condenses into water droplets and forms clouds. Sooner or later, the water returns to earth in the form of rain, snow, sleet or hail. When water strikes the earth, some of it returns to vapor through evaporation and some of it enters brooks, creeks, streams, and rivers. Eventually, this water makes its way into the oceans. Water also seeps into the ground, becoming groundwater. It moves slowly until it reaches rivers or lakes or drains into large underground areas called aquifers.
An angler should know about water temperature. In spring, water temperature rises very slowly. Water warms and cools more slowly than air. Although the air temperature may be warm, the water in some areas may still be too cold for some kinds of fish. Late in the year, the opposite may be true. In fall, water temperature drops very slowly. The air may be chilly, but the water temperature may still be warm. Fish are more active in warmer water than in cold water. Thus, when fishing in colder water, anglers should work their baits and retrieve line more slowly.
Another interesting fact is that cold water is not always heavier than warm water. Water continues to get heavier as it cools, until it reaches a temperature of 39.2 degrees Fahrenheit. At this temperature, one cubic foot of water weighs more than 62 pounds. Then, something unusual happens. Water colder than 39 degrees Fahrenheit begins to get lighter. No other liquid acts this way. What does this mean to us? Well, if water colder than 39 degrees Fahrenheit did not get lighter, ice wouldn't float. Instead, ice would form on the bottom of a lake and kill fish and other life in the water. The fact that water gets lighter before it freezes is important in deep northern lakes.
As the sun melts ice on a lake in spring and begins to heat the surface water, a change takes place. When the surface water begins to warm, it sinks to the bottom helped by wind and currents. This pushes colder water from the bottom toward the surface. This mixing of water is called "turnover." Turnover often occurs in the spring and fall. After the turnover, the water temperature of the mixed water is nearly the same throughout the lake. During this period fish are likely to be scattered and at any depth.
In summer, however, something else occurs on many deep or large lakes. The water forms three layers, each with a different range of temperatures. The sun warms the top layer (epilimnion) of water faster than the wind can mix it. Another layer (hypolimnion) is the heavy cold water at the bottom of the lake. This layer may have very little oxygen. The third layer is a narrow one that separates the top and bottom layers, called the "metalimnione," and contains a thermocline. Here the water temperature changes rapidly with only small changes in depth. Why is knowing about these layers important? One reason is that the bottom layer in some lakes has little oxygen. This forces fish to move to a higher level and into the metalimnion, near the thermocline. So in summer on lakes that separate into layers, fish will frequently move to the epilimnion to feed and then return to their preferred temperatures near the thermocline. Freshwater lakes are not the only places where water forms into layers. It also happens in saltwater estuaries and in the oceans.
We need to make sure that we keep our waters clean and free from pollution. For fish and other animals to live and thrive, the quality of water is very important. When harmful things enter our waters, the waters become polluted. Polluted water cannot be used for drinking, swimming, or fishing. The key lies in eliminating pollution. Fortunately, you can make a difference!
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