Assessment and Mapping of Water Quality of a Shallow Aquifer near an Industrial Belt using Hydro-chemical Parameters and Irrigation Water Quality Index

Abstract

Irrigation water quality issues arising from salt water intrusion or industrial pollution are experienced in many parts of Kerala state. This study was undertaken at Eloor, near Cochin, which is under the threat of industrial pollution, with the twin objectives of assessing the shallow groundwater quality of an area, and to evaluate the performance of Irrigation Water Quality Index (IWQI) as compared to hydro-chemical parameters. Water samples collected from 10 open wells during three different seasons for two years were analysed, and physico-chemical characteristics of water viz., Electrical Conductivity (EC), Sodium (Na), Potassium (K), Calcium (Ca), Magnesium (Mg), Chloride (Cl), Carbonate (CO3), and Bicarbonate (HCO3) were determined. Sodium Adsorption Ratio (SAR), Kelly Index (KI), Sodium Percentage (Na%), and Residual Sodium Carbonate (RSC) were calculated. Further, the combined measure IWQI was also computed. The study revealed that groundwater in many parts of Eloor was of poor quality with serious quality concerns during pre-monsoon season, where the IWQI of less than 70 was seen in about 85% of the geographical area. There were wide differences between the water quality indications given by single hydro-chemical methods and the combined hydro-chemical method. The spatial interpolation of EC values suggested that groundwater over the entire region is suitable for irrigation, while as per SAR classifications only 10% of the study area has water unfit for irrigation. The IWQI indicated that 70% of the area has poor quality of irrigation water. The study showed that IWQI combines the inferences from all individual hydro-chemical parameters, and IWQI should preferably be used to provide better and more comprehensive assessment of the irrigation water quality and for informed decision on suitability of water for irrigation planning and management.