A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science, School of Engineering and Technology

Thesis (M.Sc.) - Asian Institute of Technology, 1985

The studied area is covered by high grade metamorphic complex of Precambrian age. Water bearing property of metamorphic rocks as aquifer depends on the amount of fractures, faults or other structural weaknesses present in the rocks. These rocks show good "rock aquifer characteristics" in this region. As the available surface water resources becoming scarce and insufficient to supply the water needs, interest in the groundwater development has increased Groundwater system of this hard rock terrain is "structurally controlled", and the deep drilling operations show that the groundwater level lies between 30-50m below the surface. 6-7m fluctuation of near-surface water table is observed. Both surface and groundwater supplies are in a state of changing and movement is affected by seasonal variation and the hydrogeological nature of lithology. Chemistry of groundwater in this area is a considerable factor as higher values of fluoride, iron and total dissolved solids are present. This high mineralization is due to the higher pressure in the subsurface, prolonged contact of subsurface water with the host rock, limited circulation of groundwater and due to the more extensive contact with mineral grains under the surface. High concentrations of fluoride ions above the permissible limit of 1.5mg/l is present in some deep well water. There is a linear statistical relationship between fluoride and calcium plus magnesium ions and between fluoride and bicarbonate ions. However to meet the demands of water supply for rural population, the present situation of extracting groundwater from fractured hard rocks through deep wells seems to be satisfied even though, careful monitoring and feed back evolution as subsurface reservoirs are not well understood nor and readily delineated as surface reservoirs.