Water Chemical Characteristics and Water Quality Evaluation of the River under the Ecological Water Replenishment: A Case Study in the Yongding River Basin in North China

Ecological water replenishment projects have been implementedinthe Yongding River (YDR) Basin since 2019 to adjust the contradictionbetween regional ecology and social development. To clarify the waterchemistry, sources of riverine solutes, and the water quality assessmentof the YDR under the ecological water replenishment, concentrationsof major ions (Na+, K+, Ca2+ Mg2+, SO4 (2-), HCO3 (-), Cl-, and NO3 (-)) of the YDR collected in August 2021 are determined. The dominantwater chemical type of the YDR water was SO4 (2-)& BULL;Cl--Na+. Anthropogenicactivities were the dominant factors affecting concentrations of riverinesolutes, making up 71% of the total cations, and the main type wasurban domestic sewage inputs. According to the evaluation of irrigationwater quality, the YDR was facing a low-level sodium hazard and moderatesalinity hazard, and the harm to soil aggregates was limited accordingto irrigation. The health threats to adult residents were limitedin YDR, while potential health risks for children remained. Ecologicalwater replenishment projects have been implemented to improve theecological function of the YDR with significant effects observed nearthe replenishment outlets, leading to a significant improvement inthe irrigation water quality. This study highlights the disturbanceof ecological replenishment to water chemical characteristics andecological restoration function to the dry-up river and provides avaluable example for further studies of water chemistry under ecologicalwater replenishment.