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Sreedevi Pagadala, National Geophysical Research Institute (India)
Shakeel Ahmed, National Geophysical Research Institute (India)
Subrahmanyam Kambhampati, National Geophysical Research Institute (India)
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Groundwater is an important natural resource, especially in arid and semi-arid regions, because surface water sources are scare. Two third of Indian continent is covered by hard rocks. In hard rocks primary porosity is absent, rainfall recharge is taking place through secondary porosity. In these areas 5-10 percent of natural rainfall recharge is taking places annually. Groundwater demand is more than annual recharge, it means groundwater is being overexploited in these areas. Artificial recharge is imperative and is more useful way for improving groundwater levels in hard rocks areas.
The study area is 60km2 situated about 30 km south of Hyderabad, A.P., India, underlain by granites of Archean age, pink and gray colour and medium to coarse grained in texture. They have undergone variable degree of weathering with depth extending upto even 20m followed by fracturing at many places. Groundwater in the area occurs under water table conditions in the weathered granite and in semi-confined conditions in the fractured granites. The depth to water level varies from 11m to 20m. The yield of the bore wells ranges from 1000 gph to 5000 gph. The groundwater is withdrawn using more than 700 bore-wells irrigating almost 70% of the area for two crops in a year. The average annual rainfall in the area is about 570 mm and most of that occur in SW monsoon periods during a few rainy days. Artificial recharge structure (defunct dug well) was selected in the southern part of the study area. A trench of about 100m in length, 1m wide and 1m deep has been made at the lowest surface levels to collect the runoff from the catchment. At the end of the trench a pit (filled with gravel, coarse pebbles etc) and a pipe to carry the collected water into the well has been made. Regular monitoring of water levels in the dug well and near by wells and the amount of rainfall were recorded through a rain gauge installed in the catchment of the experimental site.
Already simulated groundwater flow model has been used for calculating artificial recharge flow in around the site. Based on the results and observation data in field we find that in that area water levels are raised 1.2 to 1.5m.
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