The study assesses the quantum of seepage to the aquifers through percolation ponds and establishes their zone of influence, and based on these, correlates the quantum of seepage to the total storage loss in the pond. The assessment of the benefits of the ponds, in terms of artificial recharge to the aquifers is done through an intensive study of two percolation ponds in Tamil Nadu.
A percolation pond is a small water harvesting structure, constructed across a natural stream or water course to harvest and impound the runoff from the catchments for a longer time, to facilitate vertical and lateral percolation of impounded water into the soil substrata, thereby recharging groundwater storage in the zone of influence of the pond.
The seepage losses from percolation ponds have been assessed by computing the water balance of the ponds. It is found that loss in storage is entirely due to percolation and evaporation. Therefore, using the available data, the inflows, evaporation losses and change in storage are calculated, and the seepage losses are assessed for each of the study ponds for various observation periods.
The seepage rates calculated on volume basis may not be representative, given the high variability in the storage capacities due to siltation. As a result, the column of water recharging the aquifers is also calculated. The zone of influence of the ponds is assessed by analyzing the response of the water table in the selected wells with recharge. For this purpose, the hydrograph of ponds & observation wells and the groundwater table contour maps are drawn for the recharge periods.
The study concludes that percolation ponds are very effective in recharging the shallow groundwater aquifers.
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