الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
 |  | from | 41 |  |  |
| | | from | 41 | | |
Abstract
Environmental problems are large scale phenomena which vary slowly in both
space and time simultaneous, and continuous monitoring of these phenomena is a
necessary pre-requisite to success full management of the limited resources of the
enviromnent and to the effective protection against many environmeral
problems.
Lakes and reservoirs can be considered as ”storage tanks” for fresh water, with
input and output points of water. The origin of Lakes could be tectonic, volcanic,
by land slides, by glacial activity, by river activity, or by wind action. It could
also be of organic origin created by changed action of plant growth .. ud
associated detritus, by short line activity or by solution (Jorgensen, 1980)(1).
In Lakes three distinct zones are generally evident:
1. The littoral zone
The shallow water region with light penetration to the bottom, often occupied by
rooted plants in natural Lakes.
2. Profundal zone
The bottom and deep water area beyond the depth of effective light penetration.
3. Limnetic zone
The open water zone to the depth of effective light penetration.