Multi-criteria decision-making and geospatial techniques for groundwater quality mapping in eastern India

Groundwater is vital for drinking, agriculture and industrial uses. Ensuring its quality through assessment is essential to meet health standards, prevent waterborne diseases and ensure safe consumption. Agriculture in the region heavily depends on groundwater for irrigation, and poor water quality can damage crops, reduce productivity, and harm soil health, leading to economic losses and food security challenges. This study assesses the suitability of groundwater for human use and irrigation by analyzing water quality parameters and calculating the groundwater quality index (GWQI) of Odisha state of India. The evaluation integrates Geographic Information System (GIS) technology with the Analytical Hierarchy Process (AHP), Frequency Ratio (FR), and Shannon’s Entropy (SE) methods. The research encompasses nine thematic layers for assessing irrigation water quality and eleven for drinking water quality. Each thematic layer was assigned a specific weight, and different methodologies were employed for each of the three techniques. The thematic maps were then converted into raster format and integrated within the ArcGIS Environment. To compute the Groundwater Quality Index (GWQI) for each method, a weighted overlay analysis technique was utilized. GWQI maps revealed that 70% of the irrigation areas were rated good by AHP, 63% moderate by FR, and 76% good by SE. For drinking water, 52% of the areas were classified as good by AHP, 75% good by FR, and 66% good by SE. Coastal areas of the state is affected by highly saline groundwater and magnesium contamination. The significant portion of the state experienced hard or very hard groundwater conditions whereas 24.03% of area affected by alkaline water. The outcomes of the three techniques were validated using the error matrix method with data from the Central Ground Water Board (CGWB). The Validation indicated the AHP model was the most accurate, with 78.7% accuracy for irrigation and 80% for drinking water. The study highlights the need for treatment and protection of groundwater in areas with poor quality.