Major Ion Chemistry of Waters and Possible Controls under Winter Irrigation in the Saline Land of Arid Regions

Abstract

To reduce downstream ecological damage, it is crucial to analyze water and salt sources in saline–alkali farmland drainage and optimize soil salt discharge. This study employs statistical, hydrochemical, and isotope methods to identify controlling factors and characteristics in water bodies during winter irrigation. The results show average TDS values of 0.59, 6.40, and 4.14 g/L for irrigation, phreatic, and drainage water. Irrigation and phreatic water mainly belong to the HCO3-Ca·Mg·Na and Cl·SO4-Na·Mg types. Na+/(Na+ + Ca2+) and Cl−/(Cl− + HCO3−) values suggest the rock–water interaction and evaporation influences in irrigation water, while evaporation primarily controls phreatic water. The main salt types include NaCl, MgSO4, Na2CO3, and CaCO3 for irrigation water and NaCl, MgSO4, Na2SO4, and CaCO3 for phreatic water. These findings lay a research basis for analyzing water and salt sources in farmland drainage during winter irrigation in saline–alkali land.