Water has a vital role in our lives. Water has domestic, irrigational and commercial use. Water is used in agricultural production, electricity generation and ecosystem management. Water has been associated with cultures of various regions and religions. Distribution and availability of freshwater around the world is not homogenous, there is spatial and temporal variation. Less than one third of the population are catching three quarters of total precipitation and two thirds are catching only one fourth of the annual precipitation in the world. Congo River and its tributaries confines only 10% of Africa’s population but annual runoff is 30% of the continent. Higher percentage of annual precipitation occurs during the summer monsoon season in India and Nepal.
Water surplus countries are located in South America, North America, Northern Europe (including Russia), South East Asia and Australasia. Middle East and North African countries are mostly water deficit. It has been estimated that 15 percentage or 34 countries will be water deficit by 2050. Inadequate supply of clean water to meet the human and environmental demand leads to water scarcity. Water scarcity can be defined in two ways: physical water scarcity and economic water scarcity.
Various studies suggested that more than a billion people live without clean drinking water. Millennium Development Goal is to halve by 2015, the proportion of people without sustainable access to safe drinking water and sanitation.