GIS-based assessment of groundwater suitability for agricultural irrigation in central Iran

Abstract

Groundwater is a critical irrigation source in arid and semi-arid regions. This study evaluated groundwater quality trends and irrigation suitability using multiple standard water quality indices and a GIS-based irrigation water quality index (IWQI) in various groundwater sources in Isfahan, Iran, from 1995 to 2024. A total of 412 wells, 306 Qanats, and 108 springs used for agricultural irrigation were analyzed. Additionally, the IWQI was applied at ten-year intervals using interpolation and overlay techniques in GIS. The results indicated that wells had the highest mean values for electrical conductivity (EC), 6033.3 mu S/cm, and total hardness (TH), 1153.3 mg/ L, but the lowest value for residual sodium bicarbonate (RSBC),-13.8. In contrast, springs recorded the highest soluble sodium percentage (SSP), 44.6. Findings indicated fluctuations in suitability levels over the study period, with a general decline in groundwater quality. According to the IWQI, groundwater sources were classified under severe and high restriction categories for irrigation use across all studied years. The IWQI classification provided a clear spatial visualization of groundwater quality, serving as a valuable decision-support tool for sustainable groundwater management and crop selection.