Water quality variation and its conditioning factors in the Three Gorges Reservoir, China

Xiaoxiao Wang,Hongyang Sun,Haijian Bing,He Zhu,Yanhong Wu,Jun Zhou,Yong Wu

doi:10.2166/wcc.2020.121

Abstract

Abstract The variation of water quality has been an issue of concern since the impoundment of the Three Gorges Reservoir (TGR). In this study, water samples from the TGR were collected in July and November 2015 and in May and July 2016 to reveal the variations of water quality and its key conditioning factors. The results showed that the concentrations of major ions, nutrients and heavy metals in the TGR's water body exhibited heterogeneous variations. Especially, the hotspot for major ions and heavy metals emerged at Chongqing downtown, and a decreasing trend from Chongqing toward the TGR dam was spatially observed. The heterogeneous variation of hydrochemistry in the TGR revealed the integrated influences of natural processes and human activities. Especially, the intense rainfall in the spring and early summer of 2016 promoted the transport of pollutants to the TGR, and further magnified the influence of large cities on the spatial variations of the hydrochemistry in the TGR. This study will give more insights into the change of water quality in large reservoirs in the context of the intense rainfall and the human activities.

Highlights

Dam construction is a global issue that contributes to the loss of river connectivity
The stratification in the mainstream of the Three Gorges Reservoir (TGR) did not occur during our study (Figures S2, S5, and S6), and the minor difference in the hydrochemical parameters between the surface and the bottom water at S6 might result from the mixture of the waters from the Yangtze River and the Wujiang River (Figure 1)
This study provided a reference for the occurrence of absorption and deposition of heavy metals associated with the fine sediment particles in the TGR

Summary

Introduction

Dam construction is a global issue that contributes to the loss of river connectivity. More than 63% of rivers in the world have lost the capacity to flow freely, which has altered the hydrological processes, transport of sediment and pollutants, and the water quality in reservoirs (Chen & Chau ; Grill et al ). The impoundment of the Three Gorges Reservoir (TGR) decreases flow velocity and leads to a lake-oriented alteration of hydrological environment, which has potential effects on the geochemical cycles of key elements and the water quality in the TGR (Bao et al ). The water quality has become an issue of wide concern in the TGR, and it is necessary to comprehensively understand the dynamic variations of potential pollutants in the TGR water column

Objectives

Methods

Findings

Discussion

Conclusion