Quality assessment of surface water and groundwater giving emphasis on water quality index and irrigational indicators in the southeastern part of Manipur Valley, north‐east India

Abstract

Water quality index (WQI) and irrigational indices for surface water and groundwater in the southeastern part of Manipur Valley in north‐east India has been examined. The water samples were collected during the pre‐monsoon season in the year 2016. Geologically, the Manipur Valley occurs as an intermontane piedmont‐alluvial plain filled with Quaternary alluvium of fluvio‐lacustrine origin. The basic chemical parameters of pH, total dissolved solids, electrical conductivity, total hardness, Cl−, HCO3−, Na+, Ca2+, Mg2+, Fe, Mn, and Zn were considered for computing water quality index for drinking water. Irrigational indices such as sodium absorption ratio, sodium percentage, Kelly's index, magnesium hazard, and residual sodium carbonate were calculated for determining the suitability for irrigational use. WQI, SAR, %Na+, KI, MH, RSC suggest that majority of the water samples are suitable for drinking and irrigational uses. They exhibit positive relations among them suggesting that these parameters are dependent over one another. About 20% of the piedmont zone groundwater are unsuitable for both drinking and agricultural purposes. The encrustation of gypsum, halite, and evaporite into the Disang shales enhances the dissolution process of ions such as Cl−, Na+, Ca2+, Mg2+ in the piedmont water leading to quality deterioration. Gibb's plots suggest that the chemical origin of water dominates with rock‐weathering process, while hydrochemical facies evolved from the initial stage to intermediate stage. Therefore, proper integrated management and development of water resources is necessary for the effective utilization water resources particularly around the piedmont zone.