Ground‐Water Pollution of the Madras Urban Aquifer, India

Abstract

Abstract Most of the water requirement for Madras is met from surface‐ and ground‐water supplies piped in from outside the city limits. However, as is the case for many cities, a certain proportion of the population, usually the poorest, is forced to rely on wells within the urban area. A study was therefore carried out to gain an idea of the inorganic quality of the water in the wells penetrating the shallow (< 20 m thick) alluvial aquifer below the city. Two general surveys of selected wells across the city indicated that relative to Indian domestic water standards, of the 93 ground‐water samples obtained, 25% exceeded the Ca limit, 11% the Mg limit, 43% the total dissolved solids limit, 14% the SO 4 limit, and 70% the NO 3 limit. As an indicator of biological contamination, the high concentrations of NO 3 (up to 1040 mg/l) are particularly worrying. A detailed survey of sites close to a city river was also undertaken. High heavy metal concentrations were detected, with As up to 0.42 mg/1, Hg to 0.02 mg/1, Pb to 1.82 mg/1, and Cd and 1.31 mg/1. Microbes have been found in several of the wells. It is clear that, as expected, the shallow ground water is grossly polluted.