The disenchantment of bore wellsNovember 18, 2006
In the 70’s, scientist advised to whomever wanted to listen to drill bore wells.
W. N.Palmquist and D. Duba published in 1974 a Comparative analysis of drilled an dug well yield. After experiments with dug and drilled well, they truely observe that the mean yield of a drilled well is much more efficient than the mean inflow rate in dug wells. They logically conclude that the modern technology has to be the favourised option. After naturally admiting that the problem of lowering of the water table currently faced by the dug wells (shallow) due to pumping will never affect the deeper drilled wells.
How can we pretend controlling the evolution of the water in the aquifere ? How can we be so sure that human activity will never impact the groundwater at deeper level?
Similarely, M. Bassapa Reddy observes in A comparative study of drilled wells and dug wells (1975) that the annual quantities of groundwater recharge and withdrawn show a quantity of 6,601.48 mm^3 groundwater available for utilisation.
Regarding that with bore wells the yield is better, the space, time and expenditure are economized, he doesn’t think further before ensuring that the trend in favour of drilled wells is a positive step toward better utilization of groundwater ressources.
In a certain extend, this is true. Bore wells have contributed in increasing the use of groundwater ressource whose potential until this time was underexploited.
Several realities regarding the use of bore wells have to be understood.
While drilling a bore wells, we go through the weathered zone until reaching the bed rock.
The bed rock is a complex formation that include layers of different characteristics. It can be as highly fractured as totally full.
The success of the borewell is thus variable, depending on the nature of the rock it drills. And even if the rock drilled is full of cracks, who knows if these cracks are full of water ? And for how long ?
Moreover, the way borewells have been overspread and overexploited in the last 30 years is for a large part responsible of the drastic lowering of the groundwater table.
They are so easy to use that we have abuse of them, wasting big quantities of water. And of course never thinking in increasing the recharging rate, as we were explosing the drawn rate.
The actual statement is unavoidable : lowering of water table, death of very old dug wells, and always more bore wells also.
We have to realise that groundwater is a publig good. Thus its yield has to be regulated. And its recharge seriously thought.
Borewell can be used but in a wise way.
And we should think in revalorizing the use of open wells that offer many advantages.