Hydro-chemical Characterisation and WQI-based Assessment of Groundwater Quality for Irrigation in Chirang District, Assam, India
Manas Jyoti Bharali
Department of Agricultural Engineering Assam University, 788011, Assam, India.
Avinash Kumar *
Department of Agricultural Engineering Assam University, 788011, Assam, India.
*Author to whom correspondence should be addressed.
Abstract
Groundwater is a vital resource for agricultural use, provided that its quality remains within permissible limits. This study evaluates groundwater quality for irrigation suitability in Chirang district, Assam using the Water Quality Index (WQI). Groundwater samples were collected from fifteen locations from open wells and tube wells across the district. In each season, three samples were collected from each location, and their mean values for 2022–2023 were used to calculate the seasonal WQI for each location. Fourteen physicochemical parameters were analysed seasonally and location-wise to compute the WQI. The results revealed that during the pre-monsoon season, 80% of samples were classified as moderate quality and 20% as poor quality. During the monsoon season, 93.3% of samples were of good quality, while 6.7% were of moderate quality. During the post-monsoon season, 46.7% of the samples were classified as good quality and 53.3% as moderate quality. The hydro-chemical data for samples plotted on Piper trilinear diagrams across the three seasons indicated that groundwater was primarily characterised by mixed alkaline-earth chemistry, with most samples belonging to the Ca–Mg–Cl water type and corresponding to the Ca–Mg–Cl–SO₄ hydro-chemical facies. The overall quality of groundwater indicates its suitability for agricultural irrigation.
Keywords: Chirang, groundwater quality, irrigation suitability, water quality index, piper trilinear diagram, hydro-chemical facies