ABSTRACT
Groundwater resources are presently relatively underexploited on the world-scale, though there may be local or even regional over exploitation in some countries. Groundwater development should be conjunctive, that is, in step with surface water exploitation. The Cauvery irrigation system in southern India practices such management; canals feed water for recharging groundwater in the wet season, and in the dry season tube wells tap the groundwater when the canals cannot meet demands. Hand-dug wells used for millennia for domestic, livestock and irrigation supply and are still probably the most widespread means of exploiting groundwater. Tube wells have a relatively high initial cost plus recurrent costs of pumping and maintenance. Generally tube wells are sited on the land that is to be irrigated so there is little need for expensive distribution systems and less water wasted than with canal supplies. Water-lifting devices, especially pumps can be costly to install and run and are prone to failure.
