Global freshwater : Urbanisation
Villages turn into towns, towns into cities and cities into metropolises, in course of time. Towns develop industries and generate employment. As a result of this, people from villages go into town, in search of jobs. Thus rural to urban migration occurs. The basic needs of the urban population increase not only as a result of natural increases in population but also due to migration of people from one place to another, especially to the towns and cities. In particular, scarcities are created in the fundamental infrastructures. It is because there has not been any concerted effort at improving supply of water. Water scarcity is thus compounded by other problems, importantly by not improving the supply position. Drinking water scarcity becomes acute because of this.
In the world today, only in a small number of cities, water sources and distribution are found commensurate with the growth of the city. When plans are made and implemented, the population overshoots the development. For example, in the metropolitan cities of New Delhi, Mumbai, Calcutta and Chennai, scarcities of water are high due to the population growth. The inability to store water at the required levels is yet another reason for scarcity in the drinking water. Drinking water for Chennai has been stored in the suburban lakes such as the Chembarapakkam, Puzhal (Redhills) and other sources. These storages are not adequate enough for storing water needed to the city of Chennai. It is because there has been a high siltation in these sources. This has considerably reduced the quantum that could be stored at any given time. As a consequence, the surface runoff as a result of rainfall flows very quickly into the sea. It is because of this reason that water has been transported over large distances, from such places as Neyveli, using the trucks and railways. The expenditure incurred in recent years in the transport of water from far off places has mounted to Rs. 1,000 million a year.
People from rural areas continuously migrate to the cities in large number in search of employment, education and other reasons. The streams that migrate to the cities find their housing in the slums because there is a general shortage of housing. This further aggravates the shortages in water supply and pressures on existing amenities, causing suffering to the people. With congestion in cities, even the most carefully planned water supply programmes are unable to provide sufficient water supply. Almost every city, in the country, has water scarcities in some months of the year that the drinking water scarcities remain a permanent crisis. Only in a small number of villages, there are quality water sources. In many Asian countries, there is no domestic or drinking water supply by individual households. In the rainy seasons, the water that flows in the rivers becomes the source for both. When the river goes dry, the wells, ponds and lakes also go dry. Hence, scarcity exists until the next rainy season. Most peninsular rivers of India are of non-perennial nature. It is for this reason that the water is impounded in dams built across the major rivers. In dry periods, water is let into the rivers from the dam. In times of monsoon failures, the dams also go dry. Industrialisation and other related developments lead to contamination of the freshwater sources.