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Lake Types
Lakes can be divided into categories based on how water
enters the lake and/or the nutrient levels and water clarity (trophic
state) of the lake.
Lake type: how does water get into your lake?
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| Fig. 1. Seepage lake |
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| Fig. 2. Groundwater drainage lake |
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| Fig. 3. Drainage lake |
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| Fig. 4. Impoundments |
Inflows to a lake come from precipitation, runoff,
groundwater flow, and in some cases surface
flow (streams and rivers). Outflows from a lake go to evaporation, and in
some cases groundwater or surface flow. Figures 1-4 illustrate the sources
of water and outflows for four main lake types:
- Seepage lakes (Fig. 1) are
the most common lake type in Wisconsin. These lakes have no surface
water inflows or outflows. Most water comes from groundwater flow.
- Groundwater drainage lakes
(Fig. 2) have no surface water inflows but do have surface water outflows.
Most water comes from groundwater flow.
- Drainage lakes (Fig. 3) have
surface water inflows and outflows; groundwater flow plays a minor role.
- Impoundments (Fig. 4) are
manmade lakes, and often act like drainage lakes.
Lake type: nutrient levels and water clarity
Lakes can be divided into three categories (trophic
states) based on a lake's nutrient and clarity levels:
 Oligotrophic
lakes are generally clear, deep and free of weeds or large
algae blooms. Though beautiful, they are low in nutrients and do not
support large fish populations. However, oligotrophic lakes often develop
a food chain capable of sustaining a very desirable fishery of large
game fish. Eutrophic
lakes are high in nutrients and support a large biomass (all
the plants and animals living in a lake). They are usually either weedy
or subject to frequent algae blooms, or both. Eutrophic lakes often
support large fish populations, but are also susceptible to oxygen depletion.
Small, shallow, eutrophic lakes are especially vulnerable to winterkill
which can reduce the number and variety of fish. Rough fish are commonly
found in eutrophic lakes. Mesotrophic
lakes lie between the oligotrophic and eutrophic stages. Devoid
of oxygen in late summer, their hypolimnions limit cold water fish and
cause phosphorus cycling from sediments.
A natural aging process occurs in all lakes, causing them
to change from oligotrophic to eutrophic over time, and eventually to
fill in. People can accelerate the eutrophication process by allowing
nutrients from agriculture, lawn fertilizers,
streets, septic systems, and urban storm drains to enter lakes.
Find out what trophic
state your lake is in
(Exits site)
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