PRESENTATION OF NWSAS

The NWSAS (North-Western Sahara Aquifer System) was taken up in a special programme started in July 1999 that covers well over 1,000,000 km2 of which 700,000 are in Algeria, 80,000 in Tunisia and 250,000 in Libya. It is composed of sedimentary deposits which, from bottom upwards, includes the Intercalary Continental and the Terminal Complex, the two main aquiferous level.

In the Algerian and Tunisian parts of the Sahara, groundwaters from these two aquifers have been harvested more and more intensively for over fifty years already. Offtake in Libya is more recent, but interest in these resources is growing as a result of population growth and lack of renewable waters.

At present estimates of annual water extraction from this basin amount to 540 hm3 in Tunisia, 1,100 hm3 in Algeria and 250 hm3 in Libya.

Efforts to intensify offtake will be continued in the coming years with over 90% of the water being used for agriculture.

Despite the immense size of these reserves, intensive use is impossible because of many constraints and limitations:

• Ergs and stretches of dunes that render a large part of the Sahara inaccessible;
• chotts and sebkhas that cause degradation of water quality;
• water salinity;
• depth of water catchement;
• pumping levels;
• soil degradation;
• investments in infrastructures;
• water extraction costs.