Groundwater quality assessment in Nalgonda District, Telangana, India: a comprehensive approach using self organizing map

The groundwater geochemistry of an aquifer depends on inter-ionic influences and numerous chemical and physical factors unique to an area. To assess the factors governing the characteristics and quality of groundwater, the present research examined groundwater quality in parts of Telangana State, utilizing 89 groundwater samples collected from the Nalgonda District during March–May 2023. A Total of 12 physicochemical parameters, including pH, TDS, Na+, K+, Ca2+, Mg2+, HCO3−, Cl−, SO42−, NO3−, F− and TH, were analyzed, where pH and TDS were measured at sites with portable handheld meters and the rest of the parameters were tested in the laboratory. The analysis detected the presence of many parameters above the standard permissible limits, indicating severe multi-pollutant contamination. An unsupervised soft computing technique, namely self-organizing map (SOM), along with other statistical tools, such as principal component analysis (PCA), saturation index (SI), and Pearson’s correlation approach, was used to identify contamination sources. The SOM recognized three clusters in which elevated groundwater chemical concentrations were related to mineral dissolution and anthropogenic activities. PCA revealed three key principal components, summarizing 85% of the variance for the identification of groundwater pollution sources, further confirming the SOM results. The results indicated that groundwater belonging to SOM-generated Cluster I was more suitable for drinking purposes than Clusters II and III. The overall groundwater quality was assessed using an entropy-based water quality index (EWQI), which showed that a considerable part of the study area had poor (22.27%) or UFD (23.32%) water quality. The EWQI results, along with extensive statistical analysis, reveal the groundwater quality status and probable health risks in the Nalgonda District, which are essential for policymakers and stakeholders to formulate successful water management and remediation strategies.