“A lake is the landscape’s most beautiful and expressive feature. It is earth’s eye; looking into which the beholder measures the depth of his own nature.” (Henry David Thoreau in Walden)
A lake is a depression in the landscape that holds water. Lakes are formed by glaciers, volcanic eruptions, the movement of the earth’s crust, and other processes. Lakes are also formed by humans when they build dams along rivers and “impound” the water into artificial lakes. A spring-fed lake is one fed by groundwater, while a drainage lake is one fed by water flowing over the land. The surface area of lakes can range in size from less than an acre to the 31,700 square miles of Lake Superior, the world’s largest fresh water lake.
Lakes are considered temporary features in the landscape because all lakes eventually disappear as they slowly fill in with soil, dead plants and fish, and other materials. This natural aging process of lakes is called eutrophication. The time this takes depends on the lake’s size, surrounding geology, ecosystem conditions, and other factors.
How Does A Lake Work?
Connections is the most important word to keep in mind when considering how a lake works. Because of connections, any change in one part of the lake’s ecosystem affects the rest. The symptoms of these effects can range from very simple ones, like a teaspoon of new algae in an area of the lake that has been clear until now, to drastic ones like floating, dead fish. To access your lake’s health is to study its connections.
Connections: Everything is connected to everything else, so know your lake’s ecosystem!
The Lake Ecosystem
The word “eco” comes from the Greek word oikos meaning home. Your lake’s ecosystem is home to many creatures like frogs, fish, insects, ducts, muskrats, crayfish, microscopic animals like daphnia, birds and people. The lake’s water, the land surrounding it, the plants, animals, and minerals, all water draining into the lake as well as the natural processes described below, are all part of the lake ecosystem. These components of the lake ecosystem interact with one another in very complex and interdependent ways.
The Properties Of Lakes
Lakes have interrelated physical, chemical and biological properties. Disruption in one property affect the other. For example, when rain washes chemical fertilizers off your lawn and into the lake, this alters the chemical properties of the lake. The altered lake chemistry can result in new conditions in the lake that may, for example, increase the growth of algae and zooplankton and help certain types of fish species prosper while others decline. Thus the changes chemistry can actually increase the biological productivity of the lake. This may not be good. Wish more fish in the lake, bottom sediments may be more easily disturbed thus affecting physical properties such as water clarity.
Lake Cycles and Processes
Lake are governed by cycles and processes. In the hydrological (or water) cycle, water moves in a roughly circular pattern. Water falls from the air (in the form of rain or snow) to the surface of the land, rivers, and lakes. The water then moves across the land and flows into the lakes and rivers or perhaps seeps through to groundwater. Finally, water returns to the air due to either 1) evaporation from lake or land surfaces or 2) transpiration from plants.
Plants, especially algae, are the foundation of the food web in a lake ecosystem. Green plants use sunlight in a process called photosynthesis to create oxygen and sugar from water and carbon dioxide. Fish and other organisms use the oxygen to breathe, and bacteria and fungi use it to decompose plant and animal matter on the bottom of the lake.
This article taken from “Your Lake & You” by the North American Lake Management Society (NALMS).