Low-Flow Variation Characteristics of Runoff in the Source Region of the South-to-North Water Diversion Project

Clarifying the low flow characteristics of runoff in the water source areas of the South-to-North Water Diversion Project (SNWDP) within the Yangtze River Basin is significant for drought disaster prevention and water resource allocation during dry years. Based on runoff series data from typical hydrological stations in the water source region of the SNWDP in the Yangtze River Basin, the study identified dry years and analyzed the low-flow patterns and characteristics of typical dry events. The results show that the eastern and central route water source areas of the project are more severely affected by extremely dry years, whereas the western route area has a higher probability of severely dry years. The identification of dry years is consistent with historical drought records. Prolonged consecutive dry events are rare in the study area, with frequent transitions between wet and dry conditions. In 2022, the middle and lower reaches of the Yangtze River experienced a “dry season during the flood period”. The Datong station registered an extremely dry year, while the Huangjiagang and Huangzhuang stations experienced moderately dry years, which may be due to the abnormal atmospheric circulation.