The Hydrochemical and Isotopic Evolution of the Surface Water and Groundwater for Impoundment in the Xiluodu Reservoir, Jinsha River, China

Ziwen Zhou,Mingwei Li,Haiyang Xu,Zhifang Zhou

doi:10.3390/su12145805

Abstract

The construction of a large reservoir with a high dam may cause irreversible changes in the water flow system and even affect the original environmental balance. Xiluodu reservoir, as a representative of the high arch dam reservoirs in China, clearly has this potential issue. Based on the monitoring data of the hydrochemistry and stable isotopes of the water (δD, δ18O) in the Xiluodu reservoir, this study presents the evolution of the hydrochemical and isotopic characteristics of the surface water and groundwater in the reservoir before and after impoundment using cluster analysis and saturation index analysis. The main cations in the reservoir water and groundwater change from Ca2+ and Mg2+ to Ca2+ and Na+, respectively, while the ratio of HCO 3 - to the total anions dropped from 0.86 to 0.7 as the main anion. The cluster analysis results show the high correlation between the groundwater and surface water before and after water impoundment. The calculation of saturation indices indicates that the hydrogeochemical process of the groundwater includes a different trend of the dissolution of minerals. The study of deuterium excess shows that the evaporation of the groundwater near the reservoir decreased after impoundment. Based on the above results and the recharge elevation, this research concludes that the interaction between the surface water and groundwater before and after impoundment is prominent and different. The groundwater replenished the river water before impoundment, while this relationship reversed after impoundment. This evolution process is caused by reservoir storage, and the drainage system and other conditions make this evolution possible. In addition, the influence of interaction evolution on the regional water decreases continuously along the dam site, and some areas even have irreversible changes.

Highlights

China is listed by the United Nations as one of the thirteen most water-scarce countries in the world
Hydrochemistry, stable isotope, Q-cluster and saturation index analyses were employed to study the evolution of the interaction between the groundwater and surface water in the Xiluodu reservoir site before and after impoundment
The hydrochemical type of the Jinsha River changed from Ca-Mg-HCO3 to Ca-Na-HCO3-Cl, while the type of the groundwater changed from Ca-Mg-HCO3 to a mixture of Ca-Na-HCO3 and Ca-Mg-SO4

Summary

Introduction

China is listed by the United Nations as one of the thirteen most water-scarce countries in the world. The impoundment of a reservoir can reverse the groundwater system around the reservoir, leading to the irreversible change of the nature of its hydraulics and hydrochemistry. It can change the stress fields of the local groundwater, and affect the balance of the original surrounding environment. There is a strong connection between groundwater and surface water, which is an essential part of analyzing the water balance and water flow systems of an area. Making the interaction between surface water and groundwater clear plays an important role in the managing quantity and quality of local water resources; it provides evidence for the evolution of regional water flow systems after the reservoir impoundment. The interaction between groundwater and surface water can be revealed by reviewing the hydrochemical and isotope evolution of groundwater and surface water [10,11,12,13,14]

Results

Discussion

Conclusion