Discussion

The following discussion focuses on how the two different approaches of artificial recharge for augmenting groundwater resources, and identifying and characterizing renewable and non-renewable deep aquifers, can prove highly useful for sustaining groundwater resources through droughts.

In the first approach it is shown that percolation ponds constructed across monsoon streams can prove highly successful by augmenting ground-water resources (Sukhija et al. 2005). It has been shown that after construction of such percolation ponds the water table during low rainfall years is much higher than the period before construction of such artificial recharge structures. During normal rainfall years the water table had even touched the ground surface. Further it has been shown that there is lot of variation in the efficiency of such structures. However, it is also demonstrated that the control of geology outweighs the climate effect. Thus if such percolation ponds are constructed in suitable geological strata, they can provide significant artificial recharge for groundwater sustenance.

From the results of the Neyveli aquifer studies, we demonstrate how and why the Neyveli aquifer is an outstanding example of an aquifer which can be utilized in extreme conditions of drought. It has been shown that Neyveli aquifer is a vast aquifer having semi-confined and confined ground-water system; the aquifer has excellent hydraulic conductivity and has a large areal extent. The aquifer has a very distinct recharge area with very young (Modern) water indicating excellent recharge conditions. The areal extent of recharge area is about 600-1000 km2 with a recharge rate of c. 110m3/year. The vastness of the aquifer is further demonstrated by the 14C age structure as it is very young age (Modern) to >30 000 years BP old (Sukhija et al. 1996b). The palaeoclimate signatures have been clearly preserved in the aquifer. It is also shown that despite continued pumping, the groundwater potential of the aquifer is still quite high. Although there is change in the hydraulic head and groundwater chloride, the changes are not alarming, demonstrating the resilient nature of the aquifer against changing climates and increasing withdrawal rate, thus making the aquifer most useful for tackling climate change.

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