Artificial recharge to groundwater is steadily assuming importance in the wake of the decline in water level in several parts of the country. Recharge through an injection well is the most suitable option of artificial recharge for semi-confined and confined aquifers, especially in urban and industrial areas as it requires little space. Recharging capacity of a well is an important criterion in deciding the number of recharge structures required for large-scale planning of artificial recharge. The present work focuses on determining the recharging capacity of a well in a semi-confined alluvial aquifer in the middle Ganga Plain, wherein it has been found that the actual recharging capacity is lesser than the product of the well-specific capacity and available pressure head.Keywords: Alluvial aquifer, groundwater, injection well, pressure head, recharging capacity.A RECHARGE well is an essential structure for recharging a confined or semi-confined aquifer. The recharge well is also referred to as an inverted well because the movement of water in it is in the reverse direction to that of a pumping well. Artificial recharge through recharge well is well suited for urban and industrial areas, as it requires little space. Experience from different parts of the world reveals that aquifers can be recharged successfully over long periods through this technique and areas with existing large-yield production wells are better suited for well injection 1 . Recharge capacity of a well is the maximum rate at which it can take in and dispose off water admitted at or near its upper end, and can be approximated by the product of the specific capacity and the available pressure head 2 . Available pressure head of a recharge well is the vertical distance between the ground surface and water level in the well. Recharge through a well takes place by forced injection. This is generally viewed as a mirror image of pumping from a well 3 . However, it has been demonstrated through field experiments that the quantum that could be injected is much less than that which could be pumped out owing to the exponential decrease in the recharge rate with time against the possible constant rate of pumping 3,4 . Decrease in the recharge rate with time is attributable to several factors like clogging of the well screens, air binding in the pores of the aquifer, incrustations of screen opening, obstruction by bacterial slime and algae, and base-exchange and other chemical reactions between source water, formation water and formation material 5 . Recharge rates have been found to vary widely from 0.2 to 2 million litres/day. Case studies documenting the actual recharge rate determined through field studies are limited from India. Artificial recharge through wells in India was attempted in 1976, where an experiment was conducted at Hansol, near Ahmedabad, to study the feasibility of adopting siphon principle to recharge over-exploited, deep confined aquifers from phreatic aquifers 4 . The present study documents the experimental findings of a forced rec...

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