The research on riverine hydrochemistry and controlling factors in the Danjiangkou Reservoir

Abstract

The riverine dissolved solids, indicating the environment information in watersheds, generally originated from rock weathering, soil erosion and anthropogenic inputs etc. The hydro-chemical characteristics of Danjiangkou Reservoir and its influencing factors after the implementation of South-to-North Water Transfer Project were discussed, based on water quality investigation from October 2017 to July 2018. The water in Danjiangkou Reservoir was moderately alkalescent, with pH ranging from 7.02 to 8.58. The dissolved oxygen, oxidation–reduction potential and conductivity had showed obviously seasonal variations. The total dissolved solids average was 176.14 ± 15.98 mg/L, which was much higher than that average of main rivers in the world. The Ca2+ concentration was the highest among cationic composition, accounting for 50% to 70% of total cations. Among the anion composition, $${\text{HCO}}_{3}^{ - }$$ concentrations accounted for more than 70% in most sampling points. Researches showed that carbonates weathering had contributed 70.1% of chemical compositions and mainly controlled the hydro-chemical characteristics. Some riverine ions were affected by silicates weathering. The 17.75% of chemical species were released into rivers by anthropogenic inputs, which proved to be the important factors affecting riverine chemical characteristics, especially in the wet season.