Get to Know the Different Types of Lakes
Living in Wisconsin most of my life, I grew up seeing hundreds of different lakes. Some looked liked bowls, others had carved out bays with islands, and others looked like just a widening of a large river. Each lake is unique with its own character, personality, and physical characteristics. Some are large, but shallow, and others are smaller, but considerably deep. Some lakes are strangely configured with water so clear it looks as though you could cup your hands for a drink. Others are discolored, cloudy, and tainted with higher levels of minerals. In northern Wisconsin or Michigan, you see lakes adjoining cold bogs that have a reddish stained color caused by tannic acid that leaches from the nearby bogs. It will range from a dirty brown to a brownish red.
In my home state we classify our lakes by the source of the water supply. According to the Wisconsin Department of Natural Resources, this is based on water sources and outflows. We'll discuss the four main categories identified by the WI DNR. The first category is the drainage lake. Delavan Lake in Walworth County, southern Wisconsin, is a prime example of a drainage lake. There is a distinct inlet and outlet. The main source of water is drainage from a stream. The Wisconsin River has many drainage lakes along its long, winding course through the state. If the lake owes 1/2 of its max depth to a dam, then it is not considered a natural lake. It's then classified as an artificial lake or impoundment. We'll dive into impounments in a later posting.
The next lake category is a seepage lake. There is no inlet or outlet, but there may be some overflow. These waterbodies are completely landlocked, and their main source of water is precipitation or runoff. Seepage lakes tend to be the smallest lakes, typically less than 100 acres and often times less than fifty acres in size. According to Wisconsin Lakes, a publication by the WI DNR, these lakes will often be supplemented by groundwater from immediate drainage areas. These types of lakes are the most common lakes in Wisconsin, caused by glaciation. "They reflect groundwater levels and rainfall patterns." During major droughts or periods of heavy rainfall, it's common for these lakes to experience significant fluctuations in water levels.
Spring lakes are another type of lake category in Wisconsin. I often hear a lot of people say their lake is "spring fed," when in reality it doesn't fall into this category in any way, shape or form. There seems to be more romance associated with spring fed lakes, being that the purest of groundwater is supposedly supplying the lake. Like seepage lakes, spring lakes have no inlet, but they usually do have an outlet. Spring lakes are typically the headwaters of streams in northern Wisconsin's northwoods.
The last category we'll dive into is drained lakes. Similar to spring lakes, there is no inlet, but there is an outlet. But unlike spring-fed lakes, drained lakes are supplemented by groundwater. Their source of water comes from precipitation and drainage from the land. They rely heavily on snowfall. Like seepage lakes, there is great fluctuation of water levels. During times of severe drought like the summer of 2012, some drained lakes' outlets dried up. Drained lakes are not very common in Wisconsin.