Water Resources

There are those who believe that water resources are distinguished from other natural sources in that they are secured in terms of their quantities on the surface of the earth, as these quantities are constantly renewed during a specified period of time due to the water cycle on the surface of the globe. Thus, the belief was that water could be used randomly and unscientifically. However, the emergence of water crises in several regions of the world due to high population growth rates and increasing water consumption led to the conclusion that these water resources are limited like other natural resources, and they are inevitably depletable.

The world’s water stock is constant over time and is estimated at about 1368 million cubic km, while the freshwater stock is estimated at 35 million cubic km, meaning that 97.5% of the global stock is salted water consisting of seas and oceans. As for what constitutes the freshwater stock on the earth and in the atmosphere are the permanent ice, renewable groundwater, and rivers. Nevertheless, it appears that the stock of freshwater on the surface of the earth is large, but there is a proportion of 69% of this stock, or about 24 million cubic km, that cannot be exploited at the present time, because it is basically a cover of permanent ice in the polar regions. The groundwater constitutes 30% of this stock, while the fresh rivers and lakes make up 0.266% of the world's stock. The water resources are unequally distributed spatially with respect to the rates of surface run-offs at their maximum and minimum limits. In Southeast Asia, it reaches 4000 mm/year and decreases in Southwest and Central Asia to 1 mm/year. The continents of Australia and Africa are the driest continents, with the exception of the Niger and Congo Basin and the Upper Nile. Although some regions of the world are characterized by a water surplus, most other regions face a water deficit and droughts.

Many water sources have become subject to pollution, especially in agricultural and industrial areas, and studies indicate that people in the future will resort to seawater to meet their water needs. In particular, if we take into account that the sources of water pollution with chemical and microbial pollutants are numerous and varied. Some of them are agricultural sources such as sewers overloaded with pesticides, fertilizers, clay, organic and inorganic materials drifting with water or floods that flow into rivers. Moreover, the residues of animal fields like excrements and dead animals are dumped into the water. Often times, it is rare for water to be unreachable by pollutants from these sources.