Assessing surface water quality for sustainable irrigation in Tarim Basin: a study in the summer irrigation period

Water quality in arid regions is a crucial determinant of sustainable social and economic development. Combining traditional hydrogeochemical methods with ordinary least squares (OLS) and geographically weighted regression modeling (GWR), the suitability of surface water irrigation in the summer irrigation period was investigated in the Tarim Basin. The results indicated that all water samples belonged to three types of water: SO₄ Cl–Ca•Mg, SO₄ Cl–Na, and HCO₃–Ca Mg. A convergence phenomenon occurred under long-term irrigation conditions, showing a similarity between the salt composition of soils and surface irrigation waters. Although the current quality of surface water is generally suitable for irrigation, the process of reverse ion exchange has a more important effect on surface water bodies and soil salinity, thereby resulting in an increase in the Na-ion content of the soil and subsequently enhancing alkaline hazards. Both the OLS and GWR models unequivocally indicate that nitrate nitrogen primarily originates from natural weathering processes and that the sources of this material exhibit spatial heterogeneity across distinct regions. The construction of irrigation reservoirs to effectively deal with agricultural water shortages will lead to a deterioration in the quality of irrigation. The overall findings suggest that the water quality can meet the irrigation needs at present, but to ensure the sustainable use of water resources in arid regions, the increasing nitrogen concentration caused by human activities and the decline in water quality caused by reservoir construction need to be addressed in future irrigation management.