multi-parameter assessment and qualitative zoning of groundwater resources to identify critical quality areas using a gis approach

This study conducts a multi-parameter assessment of groundwater quality in chaharmahal and bakhtiari province, iran, to identify critical zones and support sustainable water resource management. groundwater, vital for potable, irrigation, and industrial needs, was evaluated using the groundwater quality index (gwqi), principal component analysis (pca), and geographic information systems (gis). data from 2015–2016, collected from multiple sampling points, included parameters like ph, ec, tds, th, na⁺, ca²⁺, mg²⁺, cl⁻, so₄², no₃⁻, and po₄³⁻. gwqi was calculated by weighting parameters against who standards, while gis mapped seasonal and spatial quality variations. pca identified key factors driving quality changes, with the first component (69.7–83.84% variance) linking salinity (ec, tds, th) and nutrient pollution (no₃⁻, po₄³⁻) to agricultural practices and evaporation, and the second (17.15–30.3% variance) reflecting k⁺, so₄²⁻, na⁺, mg²⁺, and cl⁻, inversely related to tds due to dilution. gwqi zonation showed good-to-excellent quality (0–50) in spring 2015, declining in autumn (50–75) due to evaporation and agricultural inputs, and improving in winter 2016 from rainfall infiltration. eastern regions consistently exhibited poorer quality. the study highlights natural (evaporation, mineral dissolution) and anthropogenic (agriculture, contamination) influences on groundwater quality, with relative stability between 2015 and 2016 but notable seasonal variability. the integrated pca, gwqi, and gis approach, applied for the first time in this region, offers a robust framework for identifying critical zones and guiding localized management strategies. biannual data and high-resolution mapping enhance methodological rigor, providing new insights into hydrogeochemical challenges and a dynamic tool for sustainable groundwater management.