07-24-2014, 02:58 PM
This is the most efficient and cost effective technique to recharge unconfined aquifer overlain by poorly permeable strata.
Recharge shaft may be dug manually if the strata is of non-caving nature. The diameter of shaft is normally more than 2 m.
The shaft should end in more permeable strata below the top impermeable strata. It may not touch water table.
The unlined shaft should be backfilled, initially with boulders/ cobbles followed by gravel and coarse sand.
In case of lined shaft the recharge water may be fed through a smaller conductor pipe reaching up to the filter pack.
These recharge structures are very useful for village ponds where shallow clay layer impedes the infiltration of water to the aquifer.
It is seen that in rainy season village tanks are fully filled up but water from these tanks does not percolate down due to siltation and tubewell and dugwells located nearby remains dried up. The water from village tanks get evaporated and is not available for the beneficial use.
By constructing recharge shaft in tanks, surplus water can be recharged to ground water. Recharge shafts of 0.5 to 3 m. diameter and 10 to 15 m. deep are constructed depending upon availability of quantum of water.
The top of shaft is kept above the tank bed level preferably at half of full supply level. These are back filled with boulders, gravels and coarse sand.
In upper portion of 1 or 2 m depth, the brick masonry work is carried out for the stability of the structure.
Through this technique all the accumulated water in village tank above 50% full supply level would be recharged to ground water. Sufficient water will continue to remain in tank for domestic use after recharge.
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Recharge shaft may be dug manually if the strata is of non-caving nature. The diameter of shaft is normally more than 2 m.
The shaft should end in more permeable strata below the top impermeable strata. It may not touch water table.
The unlined shaft should be backfilled, initially with boulders/ cobbles followed by gravel and coarse sand.
In case of lined shaft the recharge water may be fed through a smaller conductor pipe reaching up to the filter pack.
These recharge structures are very useful for village ponds where shallow clay layer impedes the infiltration of water to the aquifer.
It is seen that in rainy season village tanks are fully filled up but water from these tanks does not percolate down due to siltation and tubewell and dugwells located nearby remains dried up. The water from village tanks get evaporated and is not available for the beneficial use.
By constructing recharge shaft in tanks, surplus water can be recharged to ground water. Recharge shafts of 0.5 to 3 m. diameter and 10 to 15 m. deep are constructed depending upon availability of quantum of water.
The top of shaft is kept above the tank bed level preferably at half of full supply level. These are back filled with boulders, gravels and coarse sand.
In upper portion of 1 or 2 m depth, the brick masonry work is carried out for the stability of the structure.
Through this technique all the accumulated water in village tank above 50% full supply level would be recharged to ground water. Sufficient water will continue to remain in tank for domestic use after recharge.