Experimental Study on Restoring Navigable Water Level in Near-dam Section Downstream of Danjiangkou during Dry Season for the Water Diversion Project from the Yangtze River to the Hanjiang River

doi:10.11988/ckyyb.20240632

Abstract

Abstract:

The water replenishment inlet of the Yangtze-to-Hanjiang River Diversion Project is located approximately 5 kilometers from Anle River outlet downstream of the Danjiangkou Dam, with the replenishment volume matching the diversion volume. The project’s impact on the waterway primarily manifests in the water reduction section. Comprehensive management is essential to restore navigable water levels during dry season. The effectiveness of the management plan was evaluated using a river engineering model, and the plan was optimized and further verified. Results indicate that, under the tailgate water levels of 86.47 meters and 85.90 meters for the 212 m³/s water reduction-replenishment plan, the water level from the diversion channel entrance to Huangjiagang decreases, while the water level downstream Huangjiagang remains unchanged. Notably, the water level at the diversion channel entrance experiences the largest drop, decreasing by 0.08 meters and 0.19 meters, respectively. After the comprehensive management plan 1 is implemented, the water level at the diversion channel entrance is reduced by 0.02 meters. However, the water level in the water-reduction section does not recover to pre-diversion levels, primarily because replenished water from the Anle River estuary fails to enter the left main waterway. Based on these experimental results, it is recommended to optimize the management plan by installing two bottom protection belts along the lower edge of the Canglangzhou outlet. Experiments identified four elevation values for these belts, with a recommendation to set the elevation at 85.5 meters. Further detailed analysis supports this elevation. The optimized plan is expected to slightly elevate the water level from the diversion channel entrance to Huangjiagang above pre-diversion levels, with a maximum increase of 0.06 meters at the channel entrance.

Key words: Water Diversion Project from the Yangtze River to the Hanjiang River, near-dam section, low water period, navigable water level, river engineering model, restoration test, comprehensive management of channel

CLC Number:

TV131.61水工模型试验

ZHU Yong-hui, GUO Xiao-hu, LI Ling-yun, WANG Yan-jun, ZHANG Dan. Experimental Study on Restoring Navigable Water Level in Near-dam Section Downstream of Danjiangkou during Dry Season for the Water Diversion Project from the Yangtze River to the Hanjiang River[J]. Journal of Changjiang River Scientific Research Institute, 2024, 41(10): 6-13.

Figures/Tables 15

Fig.1 Schematic diagram of the outlet section of the water conveyance tunnel of the Yangtze-to-Hanjiang River Water Diversion Project

Fig.2 Changes of navigation depth in the near-dam section from 2005 to 2020

Table 1 Changes in the amount of scouring and silting in the near-dam section of Danjiangkou Reservoir from 2005 to 2020

河段范围	时段	冲淤量/(万m³)	平均冲深/m
坝址— 步行桥	2005-03—2011-11	-15.3	-0.05
	2011-11—2016-12	-5.2	-0.02
	2016-12—2020-03	-16.0	-0.06
步行桥— 汉江大桥	2005-03—2011-11	-11.2	-0.05
	2011-11—2016-12	10.5	0.05
	2016-12—2020-03	-16.2	-0.07
整个河段	2005-03—2011-11	-26.5	-0.05
	2011-11—2016-12	5.3	0.01
	2016-12—2020-03	-32.2	-0.06

Fig.3 Changes in erosion and siltation of typical sections from 2005 to 2020

Fig.4 Layout of the fixed-bed model of the near-dam section downstream of Danjiangkou Reservoir for the Yangtze-to-Hanjiang River Water Diversion Project

Table 2 Scales of the fixed-bed model

相似条件	比尺名称	比尺
几何相似	平面比尺	1∶200
几何相似	垂直比尺	1∶100
水流运动相似	流量比尺	1∶200 000
	糙率比尺	1∶1.52
	流速比尺	1∶10

Table 3 Water flow conditions of the fixed-bed model test

组次	工况	干流河道流量/ (m³·s^-1)	安乐河补水流量/ (m³·s^-1)	尾门水位/m
1	方案前	490	0	86.47
2	方案前	490	0	85.90
3	减水-补水方案后	278	212	86.47
4	减水-补水方案后	278	212	85.90

Fig.5 Changes in water level in the test river section before and after the implementation of reducing water intake and increasing water replenishment by 212 m3/s

Fig.6 Plan layout of comprehensive management scheme

Fig.7 Changes in water level before and after the implementation of management plan 1 in the test section after reducing water intake and increasing water replenishment by 212 m3/s

Fig.8 Layout of two newly arranged bottom protection belts at the lower edge of Canglangzhou outlet

Table 4 Test conditions for two bottom protection belts under different elevations

组次	工况	干流河道流量/ (m³·s^-1)	安乐河补水流量/(m³·s^-1)	尾门水位/m	护底带高程/m
1	调水后	278	212	85.90	85.0、85.2、 85.5、85.7
2	调水后	278	212	86.47	85.0、85.2、 85.5、85.7

Fig.9 Water level changes in the test section with different crest elevations of the two bottom protection belts

Fig.10 Water level changes in the test section with different crest elevations of the two bottom protection belts at different positions

Fig.11 Variation of flow velocity in typical section after the implementation of management plan Ⅱ(water reduction-replenishment 212 m3/s,and tailgate water level 85.9 m)

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