Abstract: Since 1990’s,the low water level of the lower reaches of the Xiangjiang River is constantly decreasing from Zhuzhou to Changsha.Due to the influence of the intensification of human activities and riverbed scouring caused by clear water released after the junction project operation,the water level in the dry season has the trend to further decline.To meet the navigation requirements,the low water level of the downstream ship lock of Changsha navigation-hydropower junction will be declined by 1.5 m.Based on the change of the low water level in the Xiangjiang River from Zhuzhou to Chenglinji,the main reason and its changing tendency of the low water level in the dry season have been analyzed.The rationality of reduction value of reserved water level has been demonstrated without considering the long-term adverse factors of the Three-Gorges Project.The slope method has been adopted to calculate the forward low water level of the downstream ship lock of the Changsha navigation-hydropower junction.Thus,the conclusion can be expressed that the reduction value of the 1.5 m reserved water level of the downstream Changsha navigation-hydropower junction is reasonable.