Derivation of surface and groundwater pollution index in the urban-industrial sector along Cauvery river to assess the quality standards

The simultaneous growth of industries and the urban sector has increased problems related to water quality both at the surface and sub-surface levels. It is necessary to assess water quality at regular intervals on local and regional scales and to identify the sources of pollution, vulnerable zones, and prevention methods. The study mainly focused on qualitative assessment of surface water to understand the overall pollution level and usage of river water for drinking, irrigation and industrial purposes. Moreover, to understand the biological productivity and eutrophication condition of the river water. The groundwater quality is assessed for drinking and irrigation purposes. The water quality assessment study was conducted on the banks of the Cauvery River, between Komaraplayam, Pallipalayam, and Nanjilkalamangalam along a 10 km stretch in the state of Tamil Nadu, India. The study area is equally occupied by industries, settlements, and agricultural practices. All three land use elements contribute a significant level of pollution to both surface and groundwater environments. Geologically, the study area is covered by hard crystalline rocks and an alluvium cover. To assess the pollution level, surface water samples were collected at different locations along the Cauvery River to evaluate the quality status through the derivation of various pollution indices, such as the comprehensive pollution index (CPI), Carlson’s trophic state index (C-TSI), eutrophication index (EI), and organic pollution index (OPI). The results obtained from the surface water samples have indicated that the river water is oligotrophic and does not exhibit eutrophication conditions. However, the OPI broadly indicated that the water quality ranges from moderately to heavily polluted, which represents the level of pollution in the water-shed area. The present study focuses on the assessment of contamination levels in groundwater aquifers. To achieve this, 37 groundwater samples were collected from borewells located on both sides of the river bank. The Nemerow Pollution Index (NPI), Drinking Water Quality Index (DWQI), and Soluble Sodium Percentage Index (SSPI) have indicated varying levels of pollution in the groundwater samples, some of which are partially unsuitable for drinking purposes. Overall, the research output has raised an alarm, signalling the need to take necessary measures to prevent contamination of the water environment and to implement proper management.