Multiple Changes in the Hydrologic Regime of the Yangtze River and the Possible Impact of Reservoirs

Feng Huang,Dayong Zhao,Nan Zhang,Lidan Guo,Xirong Ma,Yao Wu,Li Ren,Ziqiang Xia

doi:10.3390/w8090408

Abstract

This paper investigates hydrologic changes in the Yangtze River using long-term daily stream flow records (1955–2013) collected from four flow gauging stations located from the upper to the lower reaches of the river. The hydrologic regime is quantified using the Indicators of Hydrologic Alteration, which statistically characterize hydrologic variation within each year. Scanning t-test is applied to analyze multiple changes in the hydrologic regime at different time scales. Then, coherency analysis is applied to identify common changes among different hydrologic indicators and across different reaches of the Yangtze River. The results point to various change patterns in the five components of hydrologic regime, including the magnitude of monthly water conditions, magnitude and duration of annual extreme water conditions, timing of annual extreme water conditions, frequency and duration of high and low pulses, and rate and frequency of water condition changes. The 32 hydrologic indicators feature multiple temporal-scale changes. Spatial variations can be observed in the hydrologic changes of the upper, middle, and lower reaches of the river. Common changes in different reaches consist of hydrologic indicators including the monthly flow in October and the low-flow indicators. The monthly flow in October is dominated by decreasing trends, while the monthly flows between January and March, the annual minimum 1/3/7/30/90-day flows, and the base flow index are characterized by increasing trends. Low pulse duration and total days of low pulses feature downward trends. The coherency analysis reveals significant relationships between the monthly flow in October and the low-flow indicators, indicating that reservoir regulation is an important factor behind the hydrologic changes.

Highlights

The hydrologic regime, which is crucial to riverine ecosystems, sets a template for ecological processes, evolutionary adaptations, and native biodiversity maintenance [1]
This study demonstrates that the strategy of coupling IHA data and scanning t‐test is effective in analyzing various changes to the hydrologic regime of the Yangtze River at different time scales
The improved coherency analysis method is effective in detecting common changes across different hydrologic series, like the coherency among the hydrologic regimes of the upper, middle, and lower reaches of the Yangtze River

Summary

Introduction

The hydrologic regime, which is crucial to riverine ecosystems, sets a template for ecological processes, evolutionary adaptations, and native biodiversity maintenance [1]. The hydrologic regime is influenced by both climate and anthropogenic activities, and many studies of worldwide hydrologic changes have considered these two factors [3,4,5,6,7,8]. Water 2016, 8, 408 activities that influence the hydrologic regime include land use [9], water diversion [10], and especially dam construction [11]. The altered hydrologic regime may influence riverine ecosystems by changing the natural habitat of native aquatic organisms, thereby affecting species structure and biodiversity; over time, these factors can influence the sustainable development of human society [12]

Methods

Results

Discussion

Conclusion