Water is an important renewable resource. It is vital to life since for all physiological activities of plants and animals. Water is essential for the survival and economic development of human resource. It covers three-fourth of earth’s surface in the form of oceans. Oceans contains about 97.5 percent of earth’s water in strongly saline condition .
The rest 2.5 percent in fresh water and all of this is not available for direct human use. Most of the fresh water is frozen as polar or glacial ice (1.97 percent). Remaining fresh water occur as ground water (0.5 percent) and water in lakes and rivers (0.02 percent), soil (0.01 percent) and atmosphere (0.01 percent).Thus, only small fraction of fresh water is available for human consumption. The distribution of fresh water in geographically uneven, varying greatly form country to country and even within a country from one region to another.
Hydro-logical cycle: it is the continuous circulation of water from surface water, through the air and to the land and back to the sea. It involves evaporation of water from oceans, lakes and rivers and transpiration of water form the vegetation, with the resulting water vapor going to the atmosphere, condensation of water vapor in the atmosphere into clouds and precipitation of water as rain or snow where by water is returned to the land. The water which has fallen on the land seeps into the soil or flows out to sea. The Hydro-Logical Cycle helps to maintain a balance in the water resources of the earth. It provides fresh water for drinking, irrigation and industry.
India is enviably endowed in respect of water resources. The country is criss-crossed with rivers and blessed with high precipitation mainly due to the south-west monsoon which accounts for 75% of the annual rainfall. The major river basin along with the medium, minor river basins account for almost 91% of the country’s entire drainage area. Potable has all along been readily available that few people consider its abundance a miracle.
Study Of Fresh Water Resources
Fresh water resources range from ponds to lakes and large rivers. It has following characteristics:
a) It is exhaustible; however it is being made available again by ocean through hydro-logical cycle.
b) Fresh water is essential for life on earth.
c) It is used by humans for consumption.
d) Fresh water is utilized by various terrestrial ecosystems.
e) It is also used in various types of industries.
f) It is used for irrigation purpose.
The Indian River System: The Rivers constitute an important natural resource as they make a great contribution to irrigation, domestic and industrial water supply, hydro power generation and inland water transport. According to size, rivers of India can be classified as follows:
Major rivers: They have catchment area of over 20,000 sq. km each. There are 14 such basins, having high rainfall (e.g., Ganga, Brahmputra, Mahanadi, Indus, Narmada etc.)
Medium Rivers: They have catchment area 2,000-20,000 sq. km. each. 44 rivers fall in this category. These have medium rainfall.
Minor Rivers: They have catchment area of less than 2,000 sq. km. each. There are large numbers of such rivers. They have low rainfall. Situated within the high precipitation area under monsoon domain, India is drained by numerous rivers falling either into the Bay of Bengal or the Arabian Sea.
Ground Water: Ground water or subsurface water occurs below the surface of earth. Ground water has a constant composition and temperature and is free from turbidity, objectionable colures and pathogenic organisms. Thus, as compared to surface water, they require very little treatment. The countries ground water resources are estimated at about 452 sq. km. it is estimated that have about 45.22 m. ha of total replenish able ground water resources every year. So that, 38.38 m. ha is used for irrigation purposes and 6.94 m. ha for the industry, Domestic Consumption Purpose etc.
Oceans are used in following aspects
a) As a source of food (e.g. fishes)
b) For the production of many useful products such as align, agar carrageen an etc.
c) For generating power from sea tides.
d) For the extraction of common salt.
e) Used in commercial navigation and shipping.
f) Mineral concentration in the form of mineral nodules can be used for the source of various minerals.