Investigation of Residence and Travel Times in a Large Floodplain Lake with Complex Lake-River Interactions: Poyang Lake (China)

Yunliang Li,Qi Zhang,Jing Yao

doi:10.3390/w7051991

Abstract

Most biochemical processes and associated water quality in lakes depends on their flushing abilities. The main objective of this study was to investigate the transport time scale in a large floodplain lake, Poyang Lake (China). A 2D hydrodynamic model (MIKE 21) was combined with dye tracer simulations to determine residence and travel times of the lake for various water level variation periods. The results indicate that Poyang Lake exhibits strong but spatially heterogeneous residence times that vary with its highly seasonal water level dynamics. Generally, the average residence times are less than 10 days along the lake’s main flow channels due to the prevailing northward flow pattern; whereas approximately 30 days were estimated during high water level conditions in the summer. The local topographically controlled flow patterns substantially increase the residence time in some bays with high spatial values of six months to one year during all water level variation periods. Depending on changes in the water level regime, the travel times from the pollution sources to the lake outlet during the high and falling water level periods (up to 32 days) are four times greater than those under the rising and low water level periods (approximately seven days).

Highlights

Lakes are vitally important components of the hydrosphere with indispensable ecological value and a large inventory of surface freshwater that is readily accessible for human consumption [1]
This study presents detailed research that contributes to a better understanding of the flushing characteristics of the large floodplain of Poyang Lake with complex water level regimes
The aim of this research was limited to revealing the spatial variability of the residence time, the seasonal behaviors of the travel time, and the water level dynamics controlling the residence and travel times

Summary

Introduction

Lakes are vitally important components of the hydrosphere with indispensable ecological value and a large inventory of surface freshwater that is readily accessible for human consumption [1]. One important physical attribute of lakes is the transport time scale (e.g., residence time, water age, flushing time, and travel time) that describes the lake’s ability to renew the water contained within it via water level regime dynamics [3,4]. The time scale concept was designed to characterize the transport processes of lakes, this scale does not have a universally accepted definition. The terms ‘residence time’ and ‘travel time’ are most commonly used to represent the time scale of the physical transport processes and to elucidate associated water quality problems in lakes and other hydrological systems [5]. A widely used concept for quantifying the residence times for lakes is known as the e-folding time [2,4,5]. The e-folding time corresponds to the time when the average concentration of contaminants in the lake is reduced to 1/e or 37% of the initial concentration [6,7,8]

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Conclusion