Assessment of Groundwater Physico-Chemical Properties and Water Quality Zonation in Udalguri District of Assam: A Geospatial and WQI-based Approach

Aims: The study aims to evaluate the groundwater quality of Udalguri district, Assam, with the application of Water Quality Index (WQI) and Geographic Information System (GIS) tools to determine its suitability for drinking purposes. Study Design: A field-based water quality assessment was carried out using 38 spatially distributed samples selected through a GIS-based random approach, supported by secondary data collection from existing records and informal field interactions. Place and Duration of Study: The investigation was conducted in Udalguri district, Assam, India. Groundwater samples were collected and analyzed, and informal interactions were conducted during the study period of 2023-2024. Methodology: A total of 38 groundwater samples were collected from different sources across the district. Nine physico-chemical parameters like pH, turbidity, hardness, alkalinity, iron, manganese, nitrate, chloride, and fluoride were analyzed following standard protocols. The WQI was computed using the weighted arithmetic index method. Spatial distribution of groundwater quality was mapped using Inverse Distance Weighted (IDW) interpolation in Geographic Information System (GIS), enabling visualization of contamination hotspots and variability across the district. Results: The findings reveal that approximately 77% of the Udalguri district falls under poor to unsuitable water quality categories. The major factors responsible for deterioration are elevated levels of iron and manganese, surpassing the Bureau of Indian Standards (BIS) permissible limits. In contrast, other parameters such as pH, hardness, nitrate, chloride, and fluoride generally remained within acceptable limits. Spatial analysis showed significant variation in contamination intensity, with certain pockets exhibiting higher risks of groundwater pollution. Conclusion: The study highlights critical groundwater quality issues in Udalguri district, emphasizing that the majority of the region’s population relies on water sources that are unsuitable for drinking without treatment. Urgent remedial measures, including water treatment initiatives, public awareness campaigns, and long-term monitoring strategies, are recommended to safeguard public health and ensure sustainable water management.