DA wahla leeewaney pak study 9th bookBook download
Chapter and author info Show + 1. Introduction Water covers more than two-thirds of the earth’s surface, but mostly salty and undrinkable. The available freshwater resource is only 2.7% of the available water on earth but only 1% of the available freshwater (in lakes, rivers and groundwater) is accessible. Most of the available freshwater resources are inaccessible because they are in the hidden part of the hydrologic cycles (deep aquifers) and in glaciers (frozen in the polar ice), which means safe drinkable water on earth has very small proportion (~3%) in the freshwater resources. Freshwater can also be obtained from the seawater by desalinization process. In some countries, sufficient freshwater is not available ( physical scarcity ). In some countries, abundant freshwater is available, but it is expensive to use ( economic scarcity ). South Africa receives about 450 mm annual rainfall and is classified as a water-stressed country [ 1 , 2 ]. The available freshwate...
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