Water resources of Wadi Hanifah, Saudi Arabia: a case study

Abstract

Although Saudi Arabia has made great progress on almost all fronts, water has always been, and still is, a serious problem. Settlement in the central area of the country is concentrated in the wadis, of which Wadi Hanifah is a good example. The Wadi descends through the central slope of the Tuwaig mountain, where Jurassic units predominate, and ends in the Al - Kharj Plain, where Cretaceous deposits outcrop. Climate is influenced to a limited extent by the relatively high altitude of the Tuwaig mountain, especially where rain fall is concerned, and an annual average of 100 mm is recorded. The rate of evaporation, however, is very high, because of the cloudless sky and high temperatures. Run-off occurs only after torrential rain, when the Wadi collects flood water from its many tributaries. Seven dams have been built in recent years in an attempt to increase underground recharge, The volume, quality and locations of underground water are determined almost entirely by climatic regime and geological characteristics. Fractions and cavities in the Jubaila limestone around Riyadh, and the alluvium deposits in the Wadi's channel used to be the main water sources. Water in these aquifers used to be at an easy reach at a depth of about 10 m beneath the surface. Urban expansion of Riyadh City, however, required a continual increase in water extraction, and the introduction of modern, equipment in agriculture also increased water consumption. This led to the lowering of the alluvium aquifer on the one hand, and the contamination of the Jubaila limestone aquifer on the other The tapping, of the Minjur aquifer in 1956 at a depth of more than 1,000 m temporarily solved the problem, but as the discharge increased sharply water level fell to a considerable depth, and in the meantime the alluvium aquifer continued dropping, so that in some areas water has been almost completely depleted. It is obvious that the lack of control over water use, and the shortage of adequate Investigation and experience, combined with the many different authorities in charge of water, produced a careless attitude to this valuable resource in both urban life and agriculture.