The effects of geological heterogeneities and piezometric fluctuations on groundwater flow and chemistry in a hard-rock aquifer, southern India | L’ impact des hétérogénéités géologiques et des fluctuations piézométriques sur l’écoulement et la chimie d’un aquifère de socle du sud de l’Inde Los efectos de las heterogeneidades geológicas y de las fluctuaciones piezométricas en el flujo y química del agua subterránea en un acuífero de roca dura en el sur de la India 印度南部坚硬岩石含水层中地质非均质性和水头波动对地下水流场及水化学的影响 Efeitos das heterogeneidades geológicas e das flutuações piezométricas no fluxo e na química da água subterrânea num aquífero fraturado do Sul da Índia
2011
Perrin, Jérôme | Ahmed, Shakeel | Hunkeler, Daniel
Crystalline aquifers of semi-arid southern India represent a vital water resource for farming communities. A field study is described that characterizes the hydrodynamic functioning of intensively exploited crystalline aquifers at local scale based on detailed well monitoring during one hydrological year. The main results show large water-table fluctuations caused by monsoon recharge and pumping, high spatial variability in well discharges, and a decrease of well yields as the water table decreases. Groundwater chemistry is also spatially variable with the existence of aquifer compartments within which mixing occurs. The observed variability and compartmentalization is explained by geological heterogeneities which play a major role in controlling groundwater flow and connectivity in the aquifer. The position of the water table within the fracture network will determine the degree of connectivity between aquifer compartments and well discharge. The presented aquifer conceptual model suggests several consequences: (1) over-exploitation leads to a drop in well discharge, (2) intensive pumping may contribute to the hydraulic containment of contaminants, (3) groundwater quality is highly variable even at local scale, (4) geological discontinuities may be used to assist in the location of drinking-supply wells, (5) modeling should integrate threshold effects due to water-table fluctuations.
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