Water is the precious natural resource, a basic human need and a prime national asset. the extent to which water is plentiful or scare , clean or polluted, beneficial or destructive, profoundly influence the extent and quality of human life.
In India, the growth of the population is about 2% per year to provide a better food intake. the competing demand of water are for irrigation , industrial products, domestic water supply, hydro power generation and environmental management.
Requirement of water for transport, recreation and fresh water fishries also require adequate provision for water. Irrigation is the application of water of soil is assist in the production of crops.
The pressure of survival and need for addition food supplies are causing the rapid expansion of irrigation throught the world . nine countries China, India, the United States of America, Pakistan, Indonesia, Mexico, Iran, Thailand and Uzbekistan have the largest irrigated areas, amounting to almost 70% of the world total irrigated area i.e. 248 Mha.
The oceans occupy about 70.8% of the earth's surface and only 29.2% is land. about 97.3% of the world water resource is in the oceans and is saline. Of the remaining 2.7% of the global fresh water resource, about 75.2% is in ice-caps and glaciers and is not able for the requirment of mankind. A major part of the balance amount amount of water occurs as groundwater, of which about 56% of the volume lies in water bearing formation deeper than 800 m below ground surface and is not ordinarily available for economical development. the amount of water available for development by men is mainly the water in the streams, rivers, lakes, and about 44% of the quantity of groundwate which occurs at depths less than 800 m from ground surface.
INDIA'S WATER BUDGET
Water resource of India are limited. the average annual rainfall of India is about 119.4 cm. this rain amounts to 392Mha-m of water. these may round off the 400Mha-m including snowfall. after allowing for evaporation losses and interception, the country's estimated water potential from surface flow is 180Mha-m. it is estimated that only about 70Mha-m of surface water can be put to beneficial use by conventional methods of development. the ultimate irrigation potential of India has been estimated at 113Mha (58Mha from major and medium irrigation projects and 55Mha from minor schemes). Our water resources are insufficient to meet long term requirement of agriculture, industry and other user, unless its judicious and economic utilization are ensured. The available resources are ill-distributed, resulting in seasonal abundance and devasting floods in some areas while large tracts in other regions are drought affected.
