Abstract: The Middle Route of China’s South to North Water Transfer Project (MR SNWTP) is one of the key engineerings to alleviate water resources crisis in the North China Plain. But water transfer from the Hanjiang River would result in changes in hydrological regimes and water use in the basin. The paper deals with the effects of different water transfer scales on the down stream of the Danjiangkou Reservoir water source of MR SNWTP. The advantages and disadvantages of three water transfer scales: 6 billion m³, 15 billion m³, and 23 billion m³ (in annual average water transfer quantity in 2020), were discussed. The effects of three scales on water tables, streamflows, navigation and irrigation were analyzed. The results demonstrated that, the scales of 1 5 billion m³ and 6 billion m³ would have small effects on the down stream of the reservoir and little change in navigation and irrigation water use, and do not need to build compensation engineerings; the scales of 15 billion m³ would have moderate effects on water tables, streamflows, navigation and irrigation, and need to build compensation engineerings for irrigation at the lower stream of the river; while the scale of 23 billion m³ would have great effects on water tables and streamflows and on irrigation and navigation, and need to compensate completely for water table decline and water quantity decrease for both irrigation and navigation.

Key words: the Middle Route of China’s South to North Water Transfer Project, water transfer effect, compensation engineering