South of the Atlas mountains in southwest Morocco, half a million people precariously farm 15,000 hectares in the plains of Tafilalt and Guelmim with supplies from a few ephemeral rivers. Daily demand is 250,000 cubic metres. During dry periods, the estimated shortfall is as high as 100,000 cubic metres a day. These are the principal questions which the first phase of the Model Project is addressing by field studies and analyses of the isotopic composition of local water. Because they are heavier, water vapour rising from the ocean to form rainclouds, have fewer of them than the seawater.
Coastal rain is therefore isotopically different from inland and different again in the mountains.
In the process water acquires telltale isotopic 'fingerprints' in different environments, and analysis of a sample, using special instruments, can reveal its 'age', origin and how it got there. Isotope hydrology techniques measure the ratios of a number of other elemental isotopes, i.e., helium, carbon, nitrogen, sulphur and chlorine. Preliminary results in Egypt appear to be promising. It has been ascertained that the shallow Nile aquifer is being replenished by the gigantic Nubian Sandstone aquifer which lies adjacent to it and at a deeper level. Ongoing studies expect to establish the rate and quantity of replenishment.