• Journal of Geographical Sciences
  • Vol. 30, Issue 5, 05000823 (2020)
SUN Zhaohua1、*, FAN Jiewei1, YAN Xin1, and XIE Cuisong2
Author Affiliations
  • 1State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China
  • 2Shanghai Water Affairs Bureau, Shanghai 200050, China
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    Abstract

    Saltwater intrusion in the estuary area threatens the use of freshwater resources. If river discharge increases to a critical value, then saltwater intrusion frequency and salinity level decreases. In this study, long-term river discharge and tidal range data in the Yangtze River Estuary (YRE) and salinity data obtained in the upper South Branch of the YRE were used to analyze the characteristics of different variables and the basic law of their interactions. Two methods, namely, the material analysis method and empirical models, were applied to determine the critical river discharge for saltwater intrusion control. Results are as follows: (1) the salinity might exceed the drinking water standard of China when the river discharge was less than 30,000 m3/s. Approximately 69% of salinity excessive days occurred when the river discharge was less than 15,000 m3/s; (2) the tidal range in the YRE roughly varied in sinusoidal pattern with a 15-day cycle length. Exponential relationship existed between daily salinity (chlorinity) and daily mean tidal range. Combining these two features with the cumulative frequency statistics of tidal ranges, it was showed that notable saltwater intrusion occurred when the tidal range was more than 2.7 m at Qinglonggang station. Moreover, the critical discharge was found to be slightly higher than 11,000 m3/s; (3) various of empirical models for salinity prediction could be chosen to calculate the critical discharge. The values obtained by different models were in the range of 11,000-12,000 m3/s; (4) the proposed critical discharge to reduce notable saltwater intrusion was 11,500 m3/s. After the Three Gorges Reservoir operation, the minimum river discharge into the YRE in 2008-2017 was below the critical discharge, thereby suggesting an increase in the minimum river discharge by reservoir regulation in drought periods.

    1 Introduction

    Estuary area is commonly densely populated and economically developed. However, the estuarine regions are also the intersections of river freshwater and marine saltwater. Such regions are prone to saltwater intrusion. Serious saltwater intrusion may affect the industrial and domestic water use, and has a negative impact on the ecological environment (Palmer et al., 2015). With the impact of various natural and anthropologic factors such as rising sea level, climate changes, increased riverine water diversions, and regulations of large-scale hydro-projects in river basin, saltwater intrusions have become important issues for many estuaries in the world (Bhuiyan et al., 2012; Jacob et al., 2013; Guerra et al., 2019; Rodrigues et al., 2019). The control and mitigation the harm of saltwater intrusion in the engineering practices of water resource utilization, not only in river basins but also in estuarine areas, have drawn remarkable concerns (Kacimov et al., 2009; Rodrigues et al., 2019).

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    Zhaohua SUN, Jiewei FAN, Xin YAN, Cuisong XIE. Analysis of critical river discharge for saltwater intrusion control in the upper South Branch of the Yangtze River Estuary[J]. Journal of Geographical Sciences, 2020, 30(5): 823
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    Category: Research Articles
    Received: Dec. 2, 2019
    Accepted: Jan. 22, 2020
    Published Online: Sep. 30, 2020
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