What type is your lake?

Your lake is different from every other, of course – no two are alike, even in a place of many lakes like Wisconsin, where I live, or Minnesota. Still, it’s possible to place lakes into categories, and there are various ways to do it – by the way they were formed, by their level of nutrients, and by how they get their water, to name a few. Let’s start with this last classification.

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 commonly 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 – and in some cases 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. (Lakes created by a dams fit the descrption of drainage lakes, although they are usually classified as impoundments). 

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.

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 precipitation and runoff. For that reason, their levels can fluctuate: high in rainy times, low during droughts. During long dry spells, the streams flowing out of these lakes may dry up. Drained lakes are the least common type 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.

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 a dense bottom sediments that hold the water in. Water levels in perched lakes can drop dramatically during long dry spells.

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