DESCRIPTION OF THE STUDY AREA AND DATA INVENTORY - Integrating GIS, Remote Sensing, and Mathematical Modelling for Surface Water Quality Management - page 89

Figure (5-3c): Potamogeton pectinatus Figure (5-3d): Eichhornia Crassipes
Fisheries
The Nile delta in Egypt is typified by a very flat topography. This has permitted the development of
shallow fish ponds bounded by earth dykes, both on the strips of land between the Mediterranean sea
and the coastal lakes (coastal howash is the common name), and within the lakes themselves (lake
shore and lake water howash). Tang (1977) reports that coastal howash typically have a salinity
between 10 and 25 ‰ and that these waters are affected by tidal action. Lake shore howash normally
have a salinity of less than 5‰ and their water level is controlled by the discharge of irrigation canals
or by pumping (personal observation). Lake howash have a salinity varying with location, and may
have a water depth of up to 2 m. These howash are generally smaller than the others.
Howash management is very simple. Between May and August, when the water level of the coastal
lakes is high due to increase of water discharge from the Nile irrigation system, the howash are
opened. Seeding takes place naturally, with tilapia, grey mullet, catfish, perch, eel, etc. The growing
period is short, as all irrigation canals are closed in January and February, and harvesting is carried out
from November to January. Commonly, poultry manure is used for fertilization, resulting in average
yields of 1475 kg/ha in the Lake Manzala region (Tang 1977). Because of the short growing period,
however, only 360 kg of this yield is suitable for human consumption, smaller fishes being used for
animal feeds. The value of the crop is, therefore, greatly reduced. With the use of supplemental feeds,
production of 3.4 t/ha are reported.
5.5. SELECTED PILOT WATERSHED ( EDKO CATCHMENT - SHALLOW LAKE SYSTEM )
5.5.1. Description of the Study Area
Edko drainage catchment and lake are selected as the components of the study watershed, to develop
the proposed integrated modelling system that could be applied to irrigated watersheds. This
watershed is a part of the Western Delta region. It is considered one of the main drainage catchments
in the western delta. It serves the North-Eastern part of the Western Delta. This watershed comprises a
total area of about 2048 km 2 including the area of the catchment and the northern lake Edko. The
watershed is located in the eastern part of the Western Delta region.
Figure (5-4) shows the Western Delta Region and the study area. The eastern edge of the area is
Rosetta Branch of the Nile. The southern edge of the area is the Noubaria Canal, and from the west the
area is bounded by Khairi drain. The north boundary of the watershed is Lake Edko.