India : underground water resources

Abstract

Irrigation is important in India where one-third of the land surface is semi-arid and the rainfall is seasonal and erratic. The irrigated area in the country has almost doubled during the last 25 years and now stands at 43 million ha. Groundwater contributes to 40 % of all irrigation. Apart from providing irrigation, groundwater has been contributing to irrigated agriculture in many other ways and has, therefore, become a vital factor in the country’s plans for agricultural development. The total usable groundwater resources of the country are assessed at 350 x 109 m3. The factors contributing to these resources and governing their occurrence and distribution in different parts of the country are described. At present about 35 % of the available resources are utilized. Different types of groundwater structures, typical to India and suited to meet the irrigation needs of small farmers, are being constructed to tap the available resources in various parts of the country. Their design and construction features, determined to a large extent by the local geological formation, are explained. The first large-scale venture in scientific planning and the development of groundwater was undertaken in 1934. A major break-through came in 1965 with the advent of high-yielding varieties of crops. Two important factors, namely the expansion of the rural electrification programme and the development of the cooperative credit structure, have helped in sustaining a high tempo of development since then. The present dimensions and other features of the development programme are indicated. A systematic programme of groundwater investigations is a must for scientific development and management of the resources. It has been greatly intensified during the recent years and investigations include hydrogeological survey, geophysical studies, exploratory drilling, pump tests, and water balance studies including the construction of mathematical models. The approach and methodology adopted to keep down the cost of investigations is described. No amount of groundwater investigation and planning will help in preventing infructuous expenditure, unless there is legislation to control and regulate groundwater development. The steps taken in this direction are mentioned.