Over ninety-seven per cent of Libya's water for agricultural and other uses came from groundwater in 1980 (Pallas). By then it was obvious that the renewable water in the coastal aquifers was seriously depleted and would not be sufficient to sustain the levels of water use implied by the national agricultural development plans. Meanwhile the potential of the southern aquifers had become apparent through their development in Kufrah, Sarir and Fezzan.The Gefara Plain has always been the major agricultural area of the country and until 1973, both before and after independence, had always attracted the bulk of public and private investment in irrigation. The decline in the level of the coastal groundwater was observed, or predicted, by all hydro-geologists who looked at the Gefara Plain after 1950, although it should be remarked that the observations were made on the basis of imprecise and unrepresentative data. Even by 1980 figures on groundwater recharge (estimated from landuse and assumed pumping levels) were numerous and inconsistent making it difficult for policy makers to determine the economies required and the measures necessary to achieve the optimum management of water resources. Depending upon which estimates of recharge and withdrawal were used, the amount by which withdrawal exceeded recharge varied from three to eight times.In these circumstances it was obviously prudent to attempt to determine the water balance from the Gefara Plain, and to this end a study was commissioned by FAO, on behalf of the Secretariat of Agriculture in Tripoli, for a study of recent satellite imagery to determine whether this inexpensive system of resources survey could make a contribution to planning water use in north-west Libya. By providing data on the irrigated area. From such data the water use element of the water balance equation could be estimated.
Virtual water evaluation for grains productsin Iran Case study: pea and bean
