Assessment of Hydro Geochemistry and Groundwater Quality for Drinking and Irrigation purposes in Coastal Aquifer of Lakshmipur district, Bangladesh: Using Fuzzy Overlay

Abstract

Areas like Bangladesh's Lakshmipur District, which have limited surface water resources, rely heavily on groundwater to meet household, industrial, and agricultural needs. To determine their physical and chemical properties, forty groundwater samples from five distinct upazilas were examined, revealing that the water quality of the area is not suitable for either drinking or agricultural purposes. Statistical methods and laboratory tests were used to interpret the seasonal and regional variations in water quality. The analysis revealed that arsenic, iron, potassium, turbidity, and TDS exceeded the permissible limits of both WHO and DoE standards in the entire samples. The biggest risks to agriculture and human health were presented by the pH, EC, and salinity problems found in 60% of the samples. In the region, groundwater often contains somewhat too much arsenic (As >0.05 mg/L); in some locations, there was excessive salinity (up to 1 ppt), turbidity (up to 271 NTU), and total dissolved solids (TDS >1000 mg/L), considering it unsuitable to drink untreated. Many samples, according to hydrogeochemical facies analysis, fall into the Na⁺-K⁺-Cl⁻-SO₄²⁻ zone (Piper), the Na⁺-K⁺ and Cl⁻ zones (Durov), and the "Rock Dominance" field (Gibbs), which indicates saline impact and rock-water interaction typical of coastal aquifers. Only a small number of sites with high water quality were shown on the WQI map created using GIS-based FO analysis; the majority were poor to inappropriate. Risks to crops and soil were highlighted by irrigation indices (SAR, RSC, MH, and Kelly's Ratio), underscoring the necessity of sustainable groundwater management.