How does your lake get its water?

You’ve read here about classifying lakes by trophic state – how poor or rich in nutrients they are. But that’s not the only way to categorize them. Another, just as interesting, is by how water gets in and out.

The number of lake types based on source of water depends partly on who is doing the defining. The Wisconsin Department of Natural Resources lists four types, but there is a fifth that many geologists mention. Here are five basic lake types found in Northern Wisconsin and Upper Michigan:

Drainage lakes. On these lakes, a stream brings water in, and a stream takes water out. That is, the lake has an inlet and an outlet. Some lakes may have more than one of each. The water level in these lakes tends to stay fairly constant. Think of a bowl into which you run a slow flow of water from the tap: An equal amount of water flows in and flows out. I live on a drainage lake and its level is largely self-regulating. In 30 years, through wet times and dry, there has been at most a foot of difference between the highest and lowest levels.

Spring lakes. These lakes have no inlet on the surface, but they do have an outlet. They get their water mainly from groundwater flowing in. Many streams originate in spring lakes, which are quite common in northern Wisconsin.

Seepage lakes. These lakes have no stream flowing in or out. Their water comes mainly from rainfall and runoff, sometimes supplemented by groundwater. Their water levels are therefore cyclical, rising and falling with wet and dry years and their effects on the water table.

Drained lakes. These lakes are like spring lakes in that they have an outlet but no surface inlet. They differ in that they are not fed by groundwater – they get their water almost solely from rainfall, snow and runoff. For that reason, their levels can fluctuate greatly. During long dry spells, the streams flowing out of these lakes may dry up. Drained lakes are uncommon here in northern Wisconsin.

Perched lakes. These lakes are truly landlocked. They have no inlet, no outlet, and no contribution from groundwater. In fact they sit on relatively high ground, above the water table, with dense bottom sediments that hold the water in. Water levels in perched lakes can drop dramatically during long dry spells.

If you want, you can add a sixth type of lake: Reservoirs. These of course are like drainage lakes in that they have a stream inlet and outlet. The difference is that they were created by humans – they wouldn’t exist if not for dams. Here in the northern Wisconsin we have the Willow, Rainbow, Turtle-Flambeau, Chippewa and other smaller flowages.  

Which type is your favorite lake? If you don’t already know, consider doing some investigating to find out.