Digital Signal Processing Reference
In-Depth Information
a Northern Estuarine System, agricultural lands, communities, urban cities, different types of land use
and various sources of pollution affecting the system, and point and non-point sources. The drains in
Delta have extremely variable quality. On the western edge of the Delta, drainage water from newly
reclaimed lands receives increased salt concentrations. Some of the Delta drains receive municipal and
industrial wastes in addition to agricultural drainage water. A large part of the drainage water is
disposed into the Northern lakes and consequently into the sea.
5.4.2.
Northern Lakes
Most of the drains in the Nile Delta discharges into lakes at the seacoast, and they, in turn, discharge to
the Mediterranean Sea. From east to west there are six terminal lakes, four of which are fed mainly by
drainage water with low salinity, these are: Lake Manzala, Burullus, Edko and Mariut. These all have
free connection to the open sea except Lake Mariut, which is permanently cut off from the sea. All the
lakes are shallow with an average salinity that ranges from 3 to 20 ppt (parts per thousands). The
remaining two lakes, Port Foad and Bardawil, are supplied only by seawater.
Part of the drainage water in Egypt is being reused for irrigation purposes by mixing with fresh
irrigation water, or diverted and used in land based aquaculture or fish farms. The principal portion of
the drainage water is directed to the northern lakes or to the sea; this estimated amount is 12.3 billion
cubic meter per year. The drainage water reuse, as a solution for irrigation water deficit, should not
decrease the drainage water flowing to the north estuarine region so as not to affect the salt balance,
the fisheries and the water quality. These impacts depend on the quantity and quality of drainage water
that is discharged to the northern lakes or to the Mediterranean Sea. The decrease in the drainage flows
in the North Delta drains due to the implementation of more reuse projects and irrigation
improvements will cause further deterioration of water quality, (Imam and Ibrahim, 1996a).
Since salt loads removed from the agricultural land will be nearly the same and the reuse of drainage
water in another irrigation application will lead to further salt build up in the drainage water. Similarly,
pollution loads discharge from municipal and industrial facilities will be mixed with less drainage
water, thereby, leading to higher concentration of pollutants.
The northern lakes at the present time are highly polluted and considered as a sink for many pollutants
such as heavy metals, pesticides, fertilizers, nutrients, and pathogens, which enter the drains through
the effluents of industrial and domestic waste water in addition to agricultural drainage water. These
lakes provide a natural environmental treatment to a considerable portion of the current contaminant
loads through sedimentation, biodegradation, plant uptake and other mechanisms, (Imam and Ibrahim,
1996a). Therefore the lakes could be considered as a protection barrier from contamination for the
beaches and coastal zones from contamination. Consequently, any further reduction in the drainage
water quantity or any further degradation in the quality would increase concentrations of pollutants
leading to a stressful environment. The overall ability of these lakes to reduce pollutants will be
damaged and may lead to an increase in the number of pollutants and contamination to the
surrounding coastal zone.
The northern lakes provide a rich environment for estuarine and marine fish. They are the most
important areas for fish production in Egypt. Now, they contribute over 50 % to fish sold in Egypt.
Fish ponds are not allowed to use canal water due to water shortage, but they can use drainage water.
The drainage water has the advantage of containing fertilizers which stimulates the primary production
of the fish ponds and consequently increases their production. On the other hand, the drainage water is
polluted with different kinds of pollutants, which are considered a risk to the fish and consumers. The
quality of water supply for the fish and aquaculture in the lakes is a very important variable, as it
mainly governs the biological productivity and the species, which can be reared. The productivity of
the water depends on the nutrient inputs in the water and the ability of the ecosystem to utilize these
Search WWH ::
Custom Search