DESCRIPTION OF THE STUDY AREA AND DATA INVENTORY - Integrating GIS, Remote Sensing, and Mathematical Modelling for Surface Water Quality Management - page 94

The Shallow Lake System current status

The Edko lake system could be defined as a wetland system of a total area about 124 km 2 estimated
from recent satellite images (ASTER 2004). This wetland system is composed of a shallow lake water
body surrounded by a water vegetation belt and a belt of aquaculture fish ponds. Satellite images taken
in 1981 indicated a loss of more than 20% of the water body through land reclamation since 1923.

1. Water body

Lake Edko is a shallow natural brackish water body situated at latitude 30 o 15 / North and longitude of
31 o 15 / East of Alexandria city, Egypt, and it extends about 19 km south of Abu-Kir Bay from the east
to west. The Lake has an average water depth between 0.8 m to 1.2 m and bed level of -0.5 m. It is
connected to the Mediterranean sea with a channel (Maadia Bougaz) of about 50.0 m width with bed
levels as deep as -6.32 m. From recent satellite images (ASTER, 2004), the calculated water body area
was about 19 km 2 , with average length of is 4 km and average width is 6 km. The deepest parts of the
lake are found at the centre of the lake where it reaches 1.4 m. the shallower areas are restricted at the
lake, margins, around the vegetation islands and near the outlet channel to the sea. The bottom
sediments of the lake are composed mainly of clay with small proportion of sand-sized sediments
mainly of calcareous shell fragments and plant debris.

2. Lake vegetation

Lake Edko is rich in vegetation of hydrophytes and amphibious, and contains several numbers of
chrysophyta, cyanophyta, and CHL-aorophyta (El Sarraf, 1976). The approximate total area of the
vegetation belt surrounding the water body is 38.66 km 2 . Inside the water body there exist a huge
number of constructed floating vegetation mats of water hyacinth and reeds collected by fishermen for
fixing the fishing nets in addition to a huge area of fishing nets blocking free navigation inside the
lake. According to a study conducted by FAO (1985) on marcrophytes, weed control and use of
aquatic plants in Lake Edko, 23 aquatic macrophytes are present in Lake Edko. This is based on plants
collected during the investigation. The most important species are the floating water hyacinths:
Eichhornia crassipes, the emergent reed Phragmites australis, and the submersed Potamogeton
pectinatus and Ceratophyllum demersum. Figure (5-8 a, b) shows the dominant types of vegetation in
the lake.

Figure (5-8a): Reeds , the dominant macrophyte in lake Edko (2005)

In areas where the water is less than 1 m deep, the reed Phragmites australis is, and was as far as
human memory goes, the dominant macrophyte. Since 1960s, water hyacinth ( Eichhornia crassipes)
has covered large areas, particularly away from the tidal influence. Submersed plants, principally
Ceratophyllum demersum and Potamogeton pectinatus , densely cover large areas of the less saline