220.127.116.11 Lakes and Streams
As may already have been discussed, lakes differ fundamentally from streams in that streams
contain flowing water and are described as lotic and lake waters are standing and are described as
lentic. A further distinction is made between saline or salt-water bodies (marine) and freshwater
bodies (lacustrine). The distinctions do not end, however, with these. Within a single lake, there are a
variety of habitats and life zones within which biota reside for some or all of their lives. These regions
often coincide, for good reasons, with physical or chemical limnological zones or regions of the lake,
betraying the fundamental interdependence of aquatic life with their physical and chemical environments
as well as among themselves.
Although the lakes managed by the Corps of Engineers are reservoirs, the comparison with
other lakes is important because original limnological principles were developed in natural lakes and
these do not always apply to reservoirs.
Lakes are shaped differently. Most people are familiar with the Great Lakes and their shape.
And there are smaller northern lakes that are almost round in shape. Lakes shaped like those also occur
in the coastal plain and in Florida. Many lakes have unusual characteristics because they were
constructed as an engineering project. These reservoirs (man-made impoundments) have dams at one
end and shallow tributary inflows at the ends of sometimes numerous `arms' of the lakes. Figure 1.2.1
illustrates the cross-sectional differences including detail of one hydroelectric dam. This is one common
characteristic of reservoirs.
Figure 1.2.1 Cross-sectional diagram of Richard B. Russell Lake showing the dam
detail and the placement of intakes and outlets