నైరూప్య

Aquifer Parameterization in an Alluvial Area: Varanasi District, Uttar Pradesh, India- A Case Study

Poonam Dubey, M.M.Singh, H.K.Pandey

The principle objective of groundwater study under reference is to estimate the aquifer parameters. Hydraulic properties of aquifers and associated layers have been determined by the pumping test which involves abstraction of water in response to the stress applied due to pumping at a known discharge rate and observing aquifer′s hydraulic head with respect to time. The nature, occurrence and availability of groundwater are directly related to relative thickness of sand and clay zones in the region. Sandy layers form the most significant aquifers in the study area. Good quality potable water is available from coarse grained deep sandy aquifers. On the basis of electrical logging interpretation, the groundwater is saline from ground level to 75.00 m mbgl. The zone from 73.00-78.00 m mbgl has been properly sealed by cement slurry. The well has been shrouded with 3-5 mm pea size gravel up to 75 m from bottom and clay was filled up to the ground surface after proper development. During the well development process by an over-pumping unit, a pumping test was conducted, which comprises of Step Drawdown Test (SDT) and Aquifer Performance Test (APT) to determine the performance, efficiency of well and hydraulic properties of the aquifer respectively. The aquifer parameters evaluated are transmissivity, hydraulic conductivity, storativity, leakage factor, leakance, hydraulic resistance and hydraulic diffusivity. The estimated data shows an appreciable significance regarding the estimation of aquifer properties. As far as the groundwater quality is concerned the groundwater samples collected during SDT is found to be satisfactory, devoid of previous salinity problem which existed earlier.