Contents preface (VII) introduction 1—37

6.4.2. Conjunctive Use
Often in the past, the development of water resources has taken place in such a manner as if surface water and ground water were two separate sources. Successful management of water resources requires adding to the two-dimensional development of surface water the third dimension of depth to include ground water.
Conjunctive use means that water lifted from below the ground is used in conjunction with canal waters. It results in the coordinated, combined, and creative exploitation of ground water and surface water so as to minimise the dislocation caused by nature’s inconsistent rainfall pattern (16). Conjunctive use implies use of surface water (from either reservoir storage or diversion works) during periods of above normal precipitation for irrigation and other activities to the extent possible and letting the balance reach the ground water storage (through artificial recharge) which would be utilised for supplementing surface water supplies during years of subnormal precipitation. Such coordinated use of surface and ground waters results in increased amount of available water, smaller surface distribution system, smaller drainage system, reduced canal linings, greater flood control, and smaller evaporation losses. There are, however, some disadvantages too in resorting to conjunctive use. These are lesser hydroelectric power, greater power requirement, need for artificial recharge, and danger of

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land subsidence. The parameters related to conjunctive use, such as cropping pattern, canal capacities, capacities and spacing of wells, drainage requirements, optimum ground water level, etc. are best determined by systems analysis to derive maximum benefits.

While studying the available water resources and the original plans of Mahi-Kadana project of Gujarat which did not include extensive use of ground water, Sarma et al. (17) proposed the conjunctive use of water. Their calculations, based on a culturable command area of 213,000 ha, indicated that the intensity of irrigation could be raised from 55 per cent (achieved in 1980–81) to 180 per cent through conjunctive use. Besides, the rise in the ground water table would also be arrested.