Lake Variability and Descriptions

WISCONSIN LAKES-PUB-FM-800 99Rev. Back to WI Lakes Book Index.

Each lake has qualities which make it unique, much like people with distinct personalities. Lakes vary based on physical characteristics, such as size, depth, configuration, chemical characteristics (such as soft versus hard water), water clarity, or the types of plant and animal life present. For example, hard water lakes have higher levels of dissolved minerals such as calcium, iron and magnesium than soft water lakes. Some lakes, especially those near acidic wetlands like bogs, are stained with tannic acid that leaches from surrounding vegetation. The water in these "tannin lakes" may range in color from a dark brown "coffee" color to light brown.

Natural lakes in Wisconsin frequently are classified by the source of water supply. Based on water source and outflows, four categories of lakes have been identified in this publication:

  1. Drainage lakes - These lakes have both an inlet and outlet where the main water source is stream drainage. Most major rivers in Wisconsin have drainage lakes along their course. Drainage lakes owing one-half of their maximum depth to a dam are considered to be artificial lakes or impoundments.
  2. Seepage lakes - These lakes do not have an inlet or an outlet, and only occasionally overflow. As landlocked waterbodies, the principal source of water is precipitation or runoff, supplemented by groundwater from the immediate drainage area. Since seepage lakes commonly reflect groundwater levels and rainfall patterns, water levels may fluctuate seasonally. Seepage lakes are the most common lake type in Wisconsin.
  3. Spring lakes - These lakes have no inlet, but do have an outlet. The primary source of water for spring lakes is groundwater flowing into the bottom of the lake from inside and outside the immediate surface drainage area. Spring lakes are the headwaters of many streams and are a fairly common type of lake in northern Wisconsin.
  4. Drained lakes - These lakes have no inlet, but like spring lakes, have a continuously flowing outlet. Drained lakes are not groundwater-fed. Their primary source of water is from precipitation and direct drainage from the surrounding land. Frequently, the water levels in drained lakes will fluctuate depending on the supply of water. Under severe conditions, the outlets from drained lakes may become intermittent. Drained lakes are the least common lake type found in Wisconsin.

Artificial Lakes

Artificial lakes are human-made bodies of water referred to as impoundments. In this publication, a lake is considered an impoundment if one-half or more of its maximum depth results from a dam or other type of control structure. An impoundment is considered a drainage lake since it has an inlet and outlet with its principal water source coming from stream drainage. Approximately 13 percent of Wisconsin's lakes fit this definition.

Lake Type Characterizations

The water quality of a lake and species of fish present are significantly influenced by the lake type. For example, drainage lakes support fish populations which are not necessarily identical to the streams connected to them. Drainage lakes, particularly impoundments, usually have higher nutrient levels than many natural seepage or spring lakes.

In contrast to drainage lakes, landlocked seepage lakes are not influenced by streams. Consequently, seepage lakes frequently have a less diverse fishery. Seepage lakes also have a smaller drainage area, which may help to account for lower nutrient levels.

Produced by: Wisconsin Department of Natural Resources, Bureau of Fisheries Management and Habitat Protection
More information on this topic: James Vennie, Limnologist, (608)266-2212

Lakes Partnership | Watershed Management | Fish Wisconsin | Fisheries Management

Last Revised: Thursday January 18 2007