Non-renewable groundwater resources: a ... - unesdoc - Unesco

CHAPTER 5 ■ REGIONAL CASESeither for large development projects in Libya or for private farms located in old traditionaloases in Egypt. Quantifying the exploitable remaining volume depends on many factors. Thesefactors include the changing cost of pumping water, the uses to which the water is put, quantitativeand qualitative reactions of the reserves to exploitation and ecological repercussions. Inthe case of shared aquifers, groundwater withdrawals from the shared resource in each countrymay produce negative reciprocal externalities. These and other factors should be considered inquantifying the volume of exploitable groundwater.Table 3 shows that the remaining volume of freshwater that can be exploited or recoveredfrom the system is about 14,500 km 3 . A relationship between annual extraction and duration ofproduction has been worked out for each country and for the total exploitable volume asshown in Figure 3.Table 4. Total recoverable fresh groundwater volumesfrom the Nubian Sandstone Aquifer System (NSAS)NUBIAN POST NUBIAN NSASREGIONMaximumallowedwater leveldecline(m)Area(km 2 )Recoverablegroundwatervolume *(km 3 )Area(km 2 )RecoverablevolumeSouth ofthe 30°N *(km 3 )Recoverablevolume *(km 3 )Unconfined partEgypt 100.00 311,861.87 2,183.03 494,039.44 3,166.36Libya 100.00 350,732.68 2,455.13 426,479.32 2,403.61Chad 100.00 232,977.04 1,630.84Sudan 100.00 373,102.44 2,611.72Total 1,268,674.03 8,880.72 920,518.76 5,569.97Confined partEgypt 200.00 375,020.93 7.50Libya 200.00 52,521.64 1.05Total 427,542.57 8.55GRANDTOTAL1,696,216.60 8889.27 920,518.76 5,569.97 14,459.24* Based on aquifer storativity of 10 –4 for the confined part and 7 x 10 –2 for the unconfined part.79