Seasonal variability of stable isotopes in the Changjiang (Yangtze) river water and its implications for natural climate and anthropogenic impacts

Peng Qian,Kai Deng,Ergang Lian,Chengfan Yang,Shangbin Xiao,Shouye Yang,Chao Li,Zhongfang Liu

doi:10.1186/s12302-020-00359-w

Abstract

BackgroundSeasonal variations of stable hydrogen and oxygen isotopes in river water can be used to indicate hydrological processes and the water cycle in the river basin. This study presents a high-resolution time series of stable oxygen isotopic record (δ18O) in the lower Changjiang (Yangtze) River mainstream and aims to investigate the regional water cycle concerning natural climate changes and anthropogenic activities.ResultsThe river water δ18O shows apparent seasonal variations, which is overall higher during the dry season and lower during the flood season. This basin-scale seasonal variation of δ18O in precipitation over the Changjiang catchment is calculated based on the long-term meteorological and hydrological data. The seasonal variation of δ18O in the lower Changjiang river water is largely constrained by monsoon-induced precipitation, but is more directly controlled by the mixing of waters from the upper reaches and the tributary lakes in the middle valley.ConclusionsThe relative contributions of waters from the upstream and tributary lakes to the lower Changjiang mainstream have been considerably altered by the construction of Three Gorges Dam via the regulation of river discharges. A comparison of river water isotopic records with water discharges from the lakes suggests that it takes about 2 weeks (~ 17 days) for the Changjiang river water to circumvent the mid-lower reaches of the catchment before traveling to the sea. This study suggests that the stable hydrogen and oxygen isotopes can be harnessed as sensitive indicators for water cycling within a large catchment that is driven primarily by natural forcing though subject to substantial human impacts.

Highlights

Seasonal variations of stable hydrogen and oxygen isotopes in river water can be used to indicate hydrological processes and the water cycle in the river basin
Seasonal variations of river water δD and δ18O in the Changjiang mainstream The δD and δ18O in the Changjiang river water in Nantong are given in Additional file 1: Table S1
The sub-basin-weighed δ18O in precipitation over the Changjiang catchment is calculated by the long-term meteorological observation data and multi-year δ18O record from global network of isotopes in precipitation” (GNIP)

Summary

Introduction

Seasonal variations of stable hydrogen and oxygen isotopes in river water can be used to indicate hydrological processes and the water cycle in the river basin. This study presents a high-resolution time series of stable oxygen isotopic record (δ18O) in the lower Changjiang (Yangtze) River mainstream and aims to investigate the regional water cycle concerning natural climate changes and anthropogenic activities. Over the past three decades, stable hydrogen (H) and oxygen (O) isotopic compositions in river water have provided deep insights into various hydrological processes and river water cycling at different spatial and temporal. It is crucial to commence with a long-term stable isotope monitoring for the collection of baseline isotopic data. The long-term stable isotopic observations in the extensive river system can improve our understanding on the sustainable management of water supply, flood–drought cycles, ecosystem, and human health in the catchments [2]

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