IMPACT ANALYSIS OF RECHARGE STRUCTURES ON DRINKING WATER WELLS USING VISUAL MODFLOW - A CASE STUDY IN THODUR VILLAGE, WALAJABAD BLOCK, KANCHEEPURAM DISTRICT OF TAMIL NADURamji Vaidhyanathan and Madhavi Ganesan
Groundwater sustainability in several parts of India is of great concern because of the increasing abstraction to meet the demands of the burgeoning population. Among the various options available to develop an optimum management plan for such places, artificial recharging structures play a vital role and their impact on the water table need to be analyzed. This study deals with the impact of recharge structures (Check dam and Recharge shafts) constructed by TWAD in a channel in Thodur Village, Walajabad Block, Kancheepuram district of Palar Basin mainly to recharge the drinking water wells. The aquifer of the study area was simulated using the 3D finite difference model, Visual MODFLOW. Calibration and validation of the model were done for the period December 2007 to December 2011 using the observed data and the results agreed with the water table elevation of observed and predicted values. R2 value was between 0.87 to 0.94 for calibration and 0.72 to 0.98 for validation. Behavior of the water table was simulated using the validated model. Five different scenarios were considered to study the impact of these recharge structures. The results from modelling showed that there was an increase in the groundwater level by 1.59m on an average due to the combined effect of these recharge structures; 1.40m due to check dam only; 1.19m due to the recharge shafts alone and by 1.20m on increasing the depth of the recharge shaft. It was also noticed that the recharging effect was highest in well 2 compared to other wells. The simulation results showed that the sustainability of groundwater is possible only when the head is maintained at the check dam and for the prevailing pumping and recharge levels.
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