There are three main types of lakes in Northern Wisconsin. They are drainage lakes, seepage lakes, and spring fed lakes. The most common type of lake is the drainage lake. A drainage lake gets its water from runoff. There are two types of runoff, groundwater runoff that is water that collects during rains and snow melts and river runoff which is essentially pooled up river water controlled by a dam. The water quality in drainage lakes can vary greatly. A deep groundwater drainage lake with a high basin can be very clean and clear, where a shallow river drainage lake is going to be dirty and murky. As a general rule, it's safe to say that deep drainage lakes are going to have much better water quality than shallow ones.
The second most common type of lake in Northern Wisconsin is the seepage lake. A seepage lake is a lake formed by rain, runoff and groundwater and does not have an inlet or an outlet. These types of lakes have inconsistent water levels. In the recent past, there has been periods of major drought in Northern Wisconsin and many seepage lakes were down five to fifteen feet. These lakes are also somewhat susceptible to flooding in years of heavy rain or snow. Seepage lakes are often very clear lakes with very clean water. The less runoff that goes into a lake, the cleaner the water will be.
The least common type of lake in Northern Wisconsin is the spring fed lake. Like seepage lakes, spring fed lakes usually have very clean water. Most spring fed lakes are less susceptible to low water levels during droughts. Because spring fed lakes always have an outlet, they are less likely to be affected by flooding. Some lakes have strong deep springs that aren't affected by times of drought and others have shallow, less powerful springs and are affected by drought. It is best to ask someone familiar with the lake what the water does during a drought. A negative about spring fed lakes with strong springs is that the ice thickness can very by a great deal. In places where there are strong springs in shallow water the ice might not be as thick as the rest of the lake. This is something to consider if you do a lot of ice fishing.