Analysis of hydrochemical characteristics and genesis of water-deficient rivers in China: a case study of the Ciyao River Basin in Shanxi Province

In order to explore the chemical water characteristics of water-scarce rivers in China, the Ciyao River basin in Shanxi Province was taken as a case study. Water samples of the mainstream and its tributaries were collected in the wet, normal, and dry seasons of 2021. The composition and spatial variation of the main ions in the water body were analyzed using the ion chromatography (IC) instrument. In addition, Pearson correlation analyses were used to evaluate relevant correlation between ion concentrations. The results showed that the overall surface water in the study area was weakly alkaline, and the content of total dissolved solids (TDS) varied greatly, ranging from 702 to 5091 mg/L, with an average of 2897 mg/L. The TDS showed a middle stream > downstream > upstream trend, and the hydrochemical type was Cl • SO4 • HCO3 – Ca • Na. The contents of most ions were significantly changed based on differences in sampling sites and seasons. Natural and human factors influence the chemical characteristics of the river. According to the Gibbs diagram and Piper diagram (Figure 3), the ionic composition of the water body in the basin is mainly affected by the joint action of rock weathering and evaporative crystallization. Carbonate rocks constitute the most significant rock weathering, followed by evaporative and silicate rocks. Wastewater from industrial enterprises, agricultural wastewater, and activities of people’s daily living also have some influence on rock weathering. Cation exchange is also important in forming chemical water components in the Ciyao River. The research results can provide technical references and a basis for regional water environment protection, water resources development and utilization, and watershed eco-hydrology research.