Tanks have been the main source of irrigation in many parts of India for centuries. India experiences extreme climate within its 329 million hectares of geographical area. The hydrological characteristic of the Indian monsoon necessitated creating storage facilities to hold the monsoon rainwater and utilize it later. With extraordinary engineering, managerial, and social skills, an extensive system of rainwater harvesting structures comprising tanks and ponds had been built and maintained by the people for centuries. Many of these multiple use structures were the nerve centers for sustenance and livelihood of the rural communities. In Karnataka, there are 36,500 tanks of varying sizes with an irrigation potential of about 0.65 m.ha. Presently, the water storage and longevity of water storage has been reduced. With a view to increase the ground water potential in command area, in the present situation, desilting of tanks is the only way to increase the storage volume and longevity of the storage of water. Impact of tank rehabilitation on ground water levels in wells/borewells was assessed by analyzing the water discharge from the borewells. The fluctuation in the ground water table was assessed by installing the piezometers in the borewells. The results indicated that, fluctuations in ground water, at the time of establishment of piezo meter the water table was 15.50 meters (from the ground level). There was slight increase in the water table (0.75 meters) in the first year of establishment (2005-06). During the second and third years, there was decline in the water table by 5.20 meters and 4.38 meters respectively. The results can be attributed to low rainfall received viz., 297mm in second and 547 mm third year against the normal rainfall of 768mm.
Keywords : Tank, desiltation, ground water table, piezometer, water discharge, command area.