Evaluation of pollution intensity in groundwater of Kashiani and Kotalipara upazila (Bangladesh) by using different indices and multivariate statistical techniques

Groundwater (GW) quality is a critical concern for safe drinking water in Bangladesh. This study aimed to evaluate the GW quality in Kashiani Upazila (KaU) and Kotalipara Upazila (KoU) of Bangladesh. A total of 35 GW samples were collected from hand tube wells at the depths of 30 m - 370 m and analyzed using Water Quality Index (WQI), Synthetic Pollution Index (SPI), Geospatial Techniques (GST), and Multivariate Statistical Techniques (MST). Key parameters, including turbidity, pH, and nitrate (NO₃⁻), met Bangladesh standards, while electrical conductivity (EC), total dissolved solids (TDS), sodium (Na), potassium (K), ammonia (NH₃), iron (Fe), and arsenic (As) exceeded recommended limits in 5.72–80.0 % of the samples. Manganese (Mn), copper (Cu), and zinc (Zn) were not detected in any sample of the two Upazila. Pearson Correlation (PC) and Principal Component Analysis (PCA) indicated that both anthropogenic and natural factors influenced GW quality. The WQI classified 2.85 % of samples as “excellent”, 57.14 % as “good”, 28.57 % as “poor”, and 11.43 % as “very poor”, whereas SPI categorized 14.28 % as “very pure”, 42.85 % as “slightly polluted”, 5.72 % as “moderately polluted”, 8.57 % as “highly polluted”, and 28.57 % as “unfit for drinking”. The results revealed that GW in KaU was largely unsafe for drinking and domestic uses, while KoU samples were generally suitable. This study emphasizes the need for proper GW management to protect public health.