Groundwater Quality Near Riverbanks and Its Suitability for Agricultural Use in Semi-Arid Regions

Abstract

Water scarcity has become one of the most pressing challenges to agricultural sustainability, particularly in arid and semi-arid regions where climate change, dam construction, and rapid population growth have intensified the pressure on water and food resources. Groundwater adjacent to rivers represents a potential supplementary resource that can re-duce reliance on restricted surface water supplies. This study assessed the hydrochemical characteristics and agricultural suitability of shallow groundwater located near the Tigris River, Iraq. Fieldwork involved monitoring four active wells and collecting samples over six periods from October 2022 to May 2023, combined with twelve soil samples from sur-rounding agricultural fields. Laboratory analyses determined key water and soil properties, including pH, electrical conductivity, major cations and anions, and a range of salinity and sodicity indices such as total dissolved solids (TDS), sodium adsorption ratio (SAR), resid-ual sodium carbonate (RSC), potential salinity (PS), magnesium ratio, Simpson ratio (SR), Jones ratio (JR), and sodium percentage (Na%). Results indicated that groundwater levels fluctuated seasonally in tandem with the Tigris River, which directly influenced salinity levels. SI values were positive, TDS values were in the high salinity class, RSC values were consistently negative, PS values were in the medium to poor category, Na% values and MR values were within acceptable limits for irrigation, and SR values were moderately to highly contaminated. Groundwater quality, according to the U.S. Salinity Laboratory classification, was categorized between the C4S1 class (very high salinity, low sodium) and the C3S1 (high salinity, low sodium). Soil analyses showed predominantly light-textured soils with mod-erate Ec and SAR values below sodicity thresholds. The combination of soil permeability and groundwater characteristics suggests that irrigation is feasible under specific manage-ment practices. The study concludes that groundwater adjacent to rivers can serve as a val-uable supplementary source for agriculture in semi-arid regions. Its use is most effective when applied to salt-tolerant crops, supported by leaching requirements, or blended with fresh water. These findings emphasize the importance of integrated groundwater manage-ment for enhancing agricultural resilience and sustainable land use under water-scarce con-ditions. Excessive extraction of groundwater near rivers can also pose long-term sustaina-bility challenges.