Geoscience Reference
In-Depth Information
dating and sediment records; section 4.5 discusses
briefly the role of future climate change from a
sedimentological perspective; and section 4.6
concerns lake management issues.
northern Africa and central Australia, lakes
are rare, whereas in other areas they dominate
the landscape, for example Sweden (Table 4.1),
other parts of Scandinavia and the northern
parts of North America and Russia. It also can
be seen from Table 4.1 that there exists a clear
relationship between number and size; there are
many more small lakes than large lakes in the
glacial landscape of Sweden.
Many schemes for classifying lakes have been
put forward over the past 50 years (e.g. OECD
1982; Nürnberg 1996; Nürnberg & Shaw 1998).
In addition to the criteria discussed below, other
criteria to classify lakes have also been used,
including the oxygen content in the water and
the species composition of the flora and fauna
(Håkanson & Boulion 2002). The aim here is to
extract some key aspects of lake classification
schemes in order to provide a framework for the
following sections of this chapter.
A trophic level classification system of lakes
is given in Table 4.3. This scheme recognizes
four trophic levels: oligotrophic, mesotrophic,
eutrophic and hypertrophic lakes. The trophic
status of a lake is usually estimated by mean
values of primary production measured for the
growing season. Note that there is a significant
overlap between the different trophic categories
in Table 4.3. For example, in low-productive
4.1.1 Lake types and classification
A fundamental question in lake management is:
'if there is a change in an important lake vari-
able, such as the phosphorus concentration, the
concentration of suspended particulate matter
(SPM) and/or lake pH (which can be related to
acid rain), will there also be changes in key func-
tional groups of organisms and changes in eco-
system function and structure?' Is it possible to
quantify and predict such changes? Lake classi-
fication systems may not in themselves provide
answers to such questions, but they can provide
a scientific framework for such analyses. Different
types of lakes have different types of sediments.
Such relationships will be discussed in this chap-
ter. To start that discussion, this section presents
different approaches to classify lakes.
Table 4.2 gives a compilation (from Hutchinson
1957) of all existing lake types on Earth, as
classified according to form-creating processes.
Most lakes are of glacial origin, i.e. they were
formed by erosional or depositional glacial activ-
ities. In many parts of the world, for example
Table 4.2
Major lake types on earth according to Hutchinson (1957).
Type
Subtype
Example
Tectonic lakes
Volcanic lakes
Basins in faults (like Lake Bajkal and Lake Tanganyika)
Maars, caldera lakes and lakes formed by damming of
lava flows
Lakes held by rockslides, mudflows and screes
Lakes on or in ice and lakes dammed by ice
Cirque lakes and fjord lakes
Lakes created by terminal, recessional or lateral moraines
Kettle lakes and thermokarst lakes
Lakes formed in caves by solution
Landslide lakes
Glacial lakes
Lakes in direct contact with ice
Glacial rock basins
Morainic and outwash lakes
Drift basins
Solution lakes
Fluvial lakes
Plunge-pool lakes
Fluviatile dams
Meander lakes
Strath lakes, lateral lakes, delta lakes and meres
Oxbow lakes and cresentic levee lakes
Basins dammed by wind-blown sand and deflation basins
Tombolo lakes and spit lakes
Phytogenic dams and coral lakes
Dams and excavations made by man
Meteorite craters
Aeolian lakes
Shoreline lakes
Organic lakes
Anthropogenic lakes
Meteorite lakes
