Recently, the excavation construction of the diversion tunnel branch of the Yellow River Guxian Water Conservancy Hub Project was carried out, marking that this major national water conservancy project has officially entered the construction stage.
　　The Guxian Project is another controlling backbone project built on the main stream of the Yellow River since the completion of the Xiaolangdi Water Conservancy Hub Project in 2001. What is the main role of this project? What are the characteristics of the project? At a press conference on the construction of the Yellow River Guxian Water Conservancy Hub Project held in Ji County, Shanxi Province that day, the relevant person in charge of the Ministry of Water Resources answered questions.
　　A key project in the Yellow River water and sediment regulation system
　　The Guxian Project is located in the northern main stream section of the middle reaches of the Yellow River, with Ji County in Shanxi Province and Yichuan County in Shaanxi Province on the left and right banks respectively. It is named after Guxian Village in Ji County.
　　"73% of the Yellow River's water volume and 60% of its sediment volume originate from the area above the Guxian Project dam site. The construction of this project will provide follow-up power for water and sediment regulation at the Xiaolangdi Reservoir and is a key project for giving full play to the overall synergy of the Yellow River water and sediment regulation system," said Wang Baoen, Vice Minister of Water Resources.
　　Wang Baoen stated that the Yellow River has little water and much sediment, and the unbalanced water-sediment relationship is the crux of the Yellow River's complexity and difficulty in governance. The follow-up power for water and sediment regulation at the Xiaolangdi Reservoir is insufficient, and the overall synergy of the water and sediment regulation system cannot be fully brought into play. To ensure the long-term peace and stability of the Yellow River, we must firmly grasp the "bull's nose" of regulating the water-sediment relationship and improve the water and sediment regulation mechanism.
　　The Guxian Project is about 450 kilometers downstream from the Xiaolangdi Reservoir and has the advantages of large storage capacity and relatively close proximity to the Xiaolangdi Reservoir. When operated jointly with it, it will enhance the follow-up power for water and sediment regulation, improve the sediment discharge efficiency of the Xiaolangdi Reservoir and the sediment transport efficiency of the downstream river channel, achieve a "1+1>2" effect, and ensure that the downstream riverbed does not rise over the long term.
　　The highest roller-compacted concrete gravity dam on red-bed foundation
　　"The Guxian Project is currently the highest-designed roller-compacted concrete gravity dam on red-bed foundation," said Shang Quanmin, Director of the Construction Department of the Ministry of Water Resources. The so-called red-bed foundation is like a thousand-layer cake, with soft and hard rocks such as siltstone, feldspathic sandstone, and claystone distributed alternately, and there are also multiple layers of bedding shear zones and argillized interlayers. In response, the project has determined to adopt comprehensive engineering measures such as deep keyways, shear-resistant tunnels, and counterweights to solve the dam's anti-sliding stability problem.
　　According to the project's operating requirements, the dam is equipped with low-level sediment discharge bottom outlets, mid-level flood discharge middle outlets, and high-level overflow surface outlets. The bottom outlets conduct water and sediment regulation at low water levels with large discharge volumes, and the surface, middle, and bottom outlets are jointly used for flood control, so as to realize comprehensive utilization of the reservoir while ensuring development tasks such as flood control and sediment reduction.
　　According to reports, the Guxian Project dam has a huge volume of concrete pouring and will be a water conservancy project with the highest roller-compacted concrete pouring intensity and the longest duration of peak pouring intensity in the world. At the same time, the concrete aggregate yard is 65 kilometers away from the Guxian Project dam site, and the terrain and geological conditions along the route are complex, making traditional transportation methods costly and low in reliability.
　　Shang Quanmin stated that in response to the characteristics and difficulties of the dam, such as large volume, great construction difficulty, high pouring intensity, and high temperature control requirements, measures such as all-factor optimization and full-process monitoring will be adopted to ensure the quality of dam construction. At the same time, belt conveyors will be used to transport aggregates, with refined design and precise monitoring, to ensure safe and smooth aggregate transportation.
　　Zhu Hongwei, Chairman of Yellow River Guxian Water Conservancy Hub Co., Ltd., stated that during the project construction process, new technologies, new materials, and new processes will be actively adopted to promote innovation in design and construction technology. At the same time, technologies such as digital measurement and testing, digital twins, and intelligent construction will be widely applied to carry out digital real-time control of the project construction process and build a full-life-cycle digital twin Guxian Project.
　　Regulating and storing water resources in the middle and lower reaches of the Yellow River
　　Li Qun, Deputy Director of the Yellow River Water Conservancy Commission of the Ministry of Water Resources, introduced that the Yellow River runoff varies greatly between years and within the year, and its temporal and spatial distribution is uneven. The areas where water comes from and where it is used do not match: 62% of the water is produced above Lanzhou in the upper reaches, while 90% of the water use is below Lanzhou. The existing projects in the middle and lower reaches of the Yellow River have insufficient water resource regulation capacity, and in dry years the runoff in the middle and lower reaches cannot meet regional water demand.
　　"The Guxian Project is located in the middle reaches of the Yellow River and has a large reservoir capacity. It can regulate water volume across years and improve the level of water resource security in the middle and lower reaches," Li Qun said. The main water supply area of the Guxian Project is the Fenwei Plain, where the land on both banks is high and the water is low, resulting in high pumping costs, low water supply reliability, and high sediment content in the water intake. After the project is completed, the current decentralized pumping can be transformed into centralized and unified water supply, fundamentally improving the water supply and irrigation conditions on both banks.
　　According to reports, most of the water supply areas in Shanxi and the Jingdong Weibei water supply area in Shaanxi will then become gravity-flow water supply areas, and the pumping head in the Yan'an water supply area will be reduced by more than 110 meters, greatly reducing water lifting costs and providing conditions for realizing large-scale and intensive water use in irrigation districts. The project draws water from above the dam, where the sediment content is low, and the later operation and maintenance costs of supporting water conveyance canal systems will be low.
　　"The construction of the Guxian Project will greatly improve the water source conditions in Shanxi and Shaanxi provinces, optimize regional water resource allocation, solve the problem of engineering-related water shortage in the water supply areas, effectively alleviate the contradiction between water supply and demand in the water supply areas, improve the level of economical and intensive utilization of water resources in Shanxi and Shaanxi provinces, and provide water security for the high-quality economic and social development of the region," Li Qun said.