• 全国中文核心期刊
  • 中国科技核心期刊
  • 美国工程索引(EI)收录期刊

Supervisor: Ministry of Water Resources of the People's Republic of China

Sponsor: Nanjing Institute of water resources, China Water Conservancy Society

Chief Editor: Zhang JianYun

Address: No.34, Hujuguan, Nanjing

Post Code: 210029

Tel: 025-85829770

Email: skxjz@nhri.cn

ISSN 1001-6791

CN 32-1309/P

Postal Code:28-146

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Articles online first have been peer-reviewed and accepted, which are not yet assigned to volumes /issues, but are citable by Digital Object Identifier (DOI).
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On Three Gorges Reservoir control water level and operating conditions in flood season
Jun WANG, Shenglian GUO
2020, 31(4): 473-480.   doi: 10.14042/j.cnki.32.1309.2020.04.001
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As the cascade reservoirs in the upper reaches of the Yangtze River have been built and put into operation, the hydrological regime and functional requirements of the Three Gorges Reservoir (TGR) have changed significantly compared with that in the design phase. The reservoir operation of maintaining a fixed flood control limited water level (FCLWL) can no longer meet the needs of the new situation. In this paper, the feasibility of the dynamic control of the operating water level of the TGR during the flood season is demonstrated by analysing the setting conditions of the FCLWL during the design phase of the TGR, excavating the characteristics of the floods and the flood encounter rules in the basin. The results show that:① The applicable condition of the 145 m FCLWL in the design stage of TGR is to cope with major floods in the basin, and the occurrence probability of the basin-wide floods is small and has obvious characteristics, which can be predicted in advance by meteorological and hydrological forecast. ② According to the types of floods in the basin, division of flood stage and encounter rules of floods, when it is predicted that a regional flood will occur, FCLWL of the TGR will be set at 145 m from the beginning of June to the end of the Meiyu period, and then the water level will be gradually increased from the end of the Meiyu period to 155m by the 20th of August. ③ With the cooperation of meteorological and hydrological forecasting and joint operation of upstream reservoir group, the operating water level of the TGR during the flood season can fluctuate around 155 m in normal years, and earlier reservoir impoundment would be feasible. ④ The dynamic control of the water level of the TGR during the flood season will not increase the risk of flood control and siltation in the reservoir area. Or rather, it is beneficial to the hydrological regime and the relationship between the rivers and lakes in the middle and lower reaches of the Yangtze River, which can significantly improve the comprehensive utilization benefits of power generation, shipping, ecological protection and water supply.
Influence of the impoundment of cascade reservoirs on the asynchronies of flood peak and sediment peak in the Three Gorges Reservoir
Wei ZHANG, Xin LI, Jinqiu REN, Bingjiang DONG
2020, 31(4): 481-490.   doi: 10.14042/j.cnki.32.1309.2020.04.002
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After impoundment of the cascade reservoirs, the incoming suspended sediment in the Three Gorges Reservoir (TGR) greatly decreased, and the asynchronous characteristics of the sediment peak and flood peak in the TGR changed simultaneously. Therefore, it is necessary to study the asynchronous characteristics of the flood peak and sediment peak and their causes, which can provide a theoretical basis for understanding the mechanism of the asynchronous characteristics of the flood peak and sediment peak and for optimizing the regulation of reservoir sediment peak discharge. The observed data of the hydrological station in the TGR from 2003 to 2018 and a theoretical analysis were used to analyse the new asynchronous characteristics of the flood peak and sediment peak in the TGR after the impoundment of the Cascade Reservoirs and to preliminarily explore the factors affecting the asynchronous changes. It was found that after the impoundment of the Cascade Reservoirs, the asynchronism of the flood peak and sediment peak in the TGR was aggravated, which revealed that the proportion of the hysteretic sediment peak increased, the propagation time of the flood peak decreased, and the propagation time of the sediment peak increased. The reasons for these changes were the source of incoming sediment being switched to the TGR, the reduction in the flood peak and the increased particle size of the suspended sediment.
Morphological evolution and dynamic mechanics of the Jiuduansha Shoal (China) during 1959—2018
Haifeng CHENG, Pei XIN, Jie LIU, Fengfeng GU, Wei WANG, Lu HAN
2020, 31(4): 491-501.   doi: 10.14042/j.cnki.32.1309.2020.04.003
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This paper studies the morphological evolution and dynamic mechanics of the Jiuduansha Shoal (China), based on analysis of bathymetric data over the last 60 years (1959—2018). The results show that from 1959 to 1990, a natural evolution trend with relatively stable accretion rates occurred for the Jiuduansha Shoal particularly in the lower intertidal zone. During the last 30 years(1990—2018), the high mudflat of 0 m above the chart datum was subjected to rapid accretion due to the plant development and the construction of the Yangtze Estuary deep-water channel regulation project. During the last 20 years(1998—2018), the low mudflat 3 m below the chart datum was affected by the decrease in the river sediment supply and the adjacent large-scale water-related projects. The accretion rates slowed down and instead sediment erosion became to occur. During this period, the sediment reduction in the river basin led the slow-accretion mudflat to move upward in the Jiuduansha Shoal. In the future, the sediment supply in the river basin may keep decreasing and maintain a lower level. The low mudflat 3 m below the chart datum in the Jiuduansha Shoal will face a risk of further erosion, and the rest will be subjected to a decreasing accretion or sediment erosion.
Driving mechanism of Sanyiqiao point bar and shoal evolution in fluctuation segment of tidal current limit in lower reaches of Yangtze River
Yunping YANG, Jinhai ZHENG, Mingjin ZHANG, Jianjun WANG, Lingling ZHU
2020, 31(4): 502-513.   doi: 10.14042/j.cnki.32.1309.2020.04.004
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A strong correlation exists between the evolution of the point bar and shoal in the fluctuation segment of the tidal current limit in the lower reaches of the Yangtze River, with simultaneous influences from the hydrodynamic force of runoff and tidal currents, sediment sources, and human activities. This segment is crucial to channel regulation and dredging maintenance. Based on analyses of riverbed scouring and silting, branch channel diversion ratio, and evolution of Sanyiqiao point bar and shoal from 1976 to 2017, the driving mechanism of the evolution of this bar and shoal was clarified. Since 2012, at a depth of 12.5 m at the Sanyiqiao point bar, the shoal-body volume has been increasing. During high rainfall years, the point bar was dominated by silting, and the designed and deep channels were dominated by scouring. In medium rainfall years, the thickness of point bar deposition was less than that in the deep channel. Wufengshan bend in the upper reaches showed a stable river regime and had the functions of blocking the river regime of the upstream Hechangzhou River segment and adjusting the branch channel diversion ratio. The relationship between siltation at the Sanyiqiao point bar and the river-regime adjustment and branch channel diversion ratio of the upstream Hechangzhou River segment was not significant. It was mainly related to the scale and process of incoming flow in the river basin as well as scouring in the upstream river segment as sediment source. During the flood season, navigation obstruction in the upper shallow area of Sanyi Bridge was greater than that during the dry season. Navigation obstruction in years with a long duration of intermediate water flow before the flood season was greater than that during the same period in flood years (flow at Datong hydrological station was 26 000—34 000 m3/s). Therefore, the flow determined the scouring and silting distribution at the point bar and shoal, whereas the duration of intermediate water flow and amount of sediment supply determined the siltation volume at the point bar and shoal, respectively, obstructing navigation.
Dynamic geomorphological environment of large tidal channels in the South Yellow Sea and its response to human activities: a case study of Xiaomiaohong tidal channel
Kefeng CHEN, Chengjie ZENG, Nairui WANG, Junhui XU
2020, 31(4): 514-523.   doi: 10.14042/j.cnki.32.1309.2020.04.005
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Due to the lack of a fixed boundary, the stability of tidal channels in radial sand ridges is more sensitive to the impact of human activities. In this study, based on high-resolution underwater topography data of the Xiaomiaohong tidal channel in the southern part of the radial sand ridges collected over the past 20 years, the morphodynamic responses to the cumulative impact of human activities are investigated and simulated by numerical modeling. Results show that the section discharges at the tail, middle, and head parts of the Xiaomiaohong tidal channel induced by reclamation, which has reached 126.09 km2 in the past 20 years, are down 14.2%, 15.79%, and 9.13%, respectively; the average current velocities were also decreased by 20—30 cm/s, 10—20 cm/s, and 5—10 cm/s, respectively. The -5 m isobath on the southern side of the Xiaomiao channel has essentially remained stable with few changes; while the -10 m isobath is expanding westward and southward. Although the reclamation projects have resulted in a decrease of tidal capacity and hydrodynamics, the erosion and deposition they cause are restricted to the areas around the projects because of their high elevation. Overall, reclamation has little effect on the stability, southward moving, and the erosion trends of the Xiaomiaohong tidal channel.
Causes of local gravel deposition in gravel-sand transition of the Middle Yangtze River under clear water scour
Haibin XIONG, Zhaohua SUN, Ming LI, Li CHEN
2020, 31(4): 524-534.   doi: 10.14042/j.cnki.32.1309.2020.04.006
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After impoundment of the Three Gorges Reservoir (TGR), channel scour is ongoing in the reaches downstream the dam and gravel erosion, transport, and deposition have occurred in some areas of the gravel-sand transition (GST) of the Yangtze River. To investigate the causes of these phenomena, field data of flow, sediment and channel topography was collected and computational analysis was performed using a 2-D hydrodynamic numerical model. Especially, the spatial distribution characteristics of the incipient diameter under various discharges in the GST were simulated and examined. Impacts of the variations in river flow and the changes in water level downstream the reach on channel adjustment were also analyzed. The following results are obtained:① The large grain size gravel (D>30 mm) can be continuously transported along the entire GST when the incoming discharge is higher than 45 000 m3/s. On the contrary, the large grain size gravel is only locally transported in some shoal sections when the discharge lower than 15 000 m3/s. The flow dynamics are relatively weak for the transport of the same size gravel when the discharge ranges from 15 000 m3/s to 45 000 m3/s. ② The number of days with floods reduced and that with low discharge increased under the effects of the TGR operation. This trend is adverse to the long-distance transport of gravel. The water level lowering downstream the GST caused erosion in areas that previously remained stable. ③ The phenomenon of the local siltation was caused by the gravel transport in the GST driven by the increasing flow dynamics in the dry season. The main cause of this phenomenon is relevant to the special morphologic structures and sedimentary environment of the GST. This type of local bed adjustment may exist in the several locations within the GST for a long time and should receive considerable attention.
Formula of movable bed roughness for the Middle Yangtze River
Xin LIU, Junqiang XIA, Meirong ZHOU, Shanshan DENG
2020, 31(4): 535-546.   doi: 10.14042/j.cnki.32.1309.2020.04.007
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The computation of movable bed roughness is an important step in morphodynamic models. After the operation of the Three Gorges Project (TGP), a dramatic decrease of sediment load entering the Middle Yangtze River (MYR) caused the processes of channel degradation and coarsening of bed material, and the variation characteristics of the movable bed roughness became more complicated. Therefore, it is necessary to propose the formula of movable bed roughness for the MYR. Based on the 1 266 runs of measurements at five hydrometric stations such as Zhicheng, Shashi, and Hankou during the period 2001—2012, Froude number (Fr) and relative water depth (h/D50) were selected as the main factors influencing the magnitude of movable bed roughness. Based on the theory of flow regime partition, the formula of movable bed roughness was established and calibrated by these measurements using the method of multiple nonlinear regression. Finally, the predictive accuracy of the proposed formula was verified against 651 runs of independent measurements at those stations from the MYR during the period 2013—2017. The results indicate that:① the alluvial resistances in the MYR are in the lower or transitional flow regime for most of the time; and ② the calculation accuracy of the proposed formula based on the flow regime partition is significantly higher than the existing formulas with the determination coefficient (R2) of 0.89. Moreover, the Manning's roughness coefficients predicted by the new formula have the errors less than ±30% for 97.7% of the measurements.
Hydraulic characteristics of partially-filled flow in circular pipe
Falong DING, Zeyu MAO
2020, 31(4): 547-555.   doi: 10.14042/j.cnki.32.1309.2020.04.008
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Partially-filled open flow in circular-shaped pipe behaves unique hydrodynamic characteristics due to the special cross-section geometry. To investigate the peculiar characteristics caused by two-sides double-curvatures, a three-dimensional numerical model, based upon RNG k-ε turbulence model and FAVOR (Fractional Area/Volume Obstacle Representation) is established, and further verified using physical experiment results. The presented numerical model is then applied to simulate partially-filled flows with different combinations of slopes and filling degrees, in order to explore the velocity distribution, wall shear stress and Reynolds shear stress. The results indicate that velocity-distribution profiles along the different vertical lines generally follow a parabolic function, and a regression expression is proposed. A unified formula for the wall shear stress along wetted perimeter with different filling degrees is presented. The results also show that the Reynolds shear stresses linearly distribute along vertical lines. The larger the filling degree and distance from mid-perpendicular are, the smaller variation gradient of the stresses is. When filling degree is greater than 0.5, due to the influences of the secondary flow, the negative Reynolds shear stress appear along the mid-perpendicular.

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