Ten Questions on Adjustable Water Volume of the Western Route of South-to-North Water Diversion Project

Abstract

The Western Route of the South-to-North Water Diversion Project is the final link to be constructed for the four-horizontal three-vertical framework of China’s national water network. The adjustable water volume in the water source areas is a focal and challenging issue in the planning and demonstration of the Western Route. This study raised ten questions related to the adjustable water volume in the water source areas of the Western Route from the aspects of water resource background conditions and evolution trends, ecological and socio-economic water demands, scales of reservoirs and water conveyance projects, as well as impacts of water diversion on water resource development and utilization, aquatic ecological environment, hydropower, and navigation in the water source areas and their lower reaches. Based on a distributed hydrological model of the upper reaches of the Yangtze River, a simulation and analysis model for calculating the adjustable water volume in water source areas of the Western Route is established to quantitatively answer the ten questions raised. The main conclusions are as follows. First, under the premise of solely satisfying ecological and socio-economic water demands within and outside the river channels of the water source areas, a plan that combines upper and lower routes presents an average adjustable water volume of 1.59×1010 m³ over multiple years, while a plan for solely constructing a lower route can reach an average adjustable water volume of 1.74×1010 m³ by constructing the Gangtuo Reservoir for coordinated operation. Second, comprehensively considering the impacts of water diversion on water balance, hydropower, and navigation, as well as their acceptability in the water source areas, the adjustable water volume is between 1.22×1010 and 1.26×1010 m³. Third, in the long term, the plan should focus on connecting and integrating the water network in the southwestern region with the main framework and major streams of the national water network of China. This will reduce the impacts of water diversion by the Western Route Project, increase the overall water supply capacity of the project, and promote its adaptability to external conditions such as climate change.

Keywords

• Western Route of South-to-North Water Diversion Project
• water source areas
• adjustable water volume
• ecological water demand
• inter-basin water transfer