3.4 Land and water management

The openings or sea inlets of the coastal lagoons are essential for flooding and ensuring a vigorous exchange of seawater between each lagoon and the Mediterranean Sea and to allow the flow of freshwater from delta lagoons to the sea. This type of management based on hydraulic engineering is a very important means for developing fisheries in the lagoons. Movements of sediments by currents and wave action along the coast cause silting of the sea openings. It was estimated that the yearly accumulation of sand in these openings in the Bardawil lagoon only amounted to about 700 cubic meters (Pisanty, 1981). Restrictions in water exchange between the lagoon and the sea resulted in an increase of salinity, inhibition of spawning migration of commercial fish species, and reduction in the available area for fish feeding and growth, thus having an adverse effect on commercial fish stocks in this lagoon.

 

Dredging of the openings is the most expensive part of the maintenance of the lagoon, amounting to 80 percent of the total cost of the up-keep. Therefore, it is important to keep the amount of dredging at a minimum, whilst maintaining favorable physical and biological conditions for a prosperous fishery. In general terms, it was agreed by experts that protective walls at the entrance of the openings should be helpful. During the last twenty years, GAFRD carried out several engineering works to improve the entry, exchange and circulation of water inside the lagoon. These works included: dredging of the channels of the Boughazes, digging of radial channels eastward and westward from each Boughaz to allow water circulation and cladding of Boughaz channel banks with stones to reduce sand accumulation and silting. 75
During the last ten years, coastal lakes lost about 25 percent of their surface area due to seizure of land in parts of the lagoons and transferring it to fish farms, silting and spreading of aquatic weeds (El-Mezyn, 2010).