4.3.1 Flood Peak and Three-day Flood Volume Changes
In this section, flood peak and three-day flood volume data recorded at the Runcheng Station in the Qinhe River Basin during the flood season from 1971 to 2006 were analyzed to investigate their characteristics during different periods. As shown in Figure 9, peak flow during the flood season demonstrated an increasing trend in the baseline period, followed by a decreasing trend in change periods I and II. Additionally, the three-day flood volume exhibited a significant decrease during the baseline period, which could be attributed to the construction of small and medium-sized reservoirs and a decrease in precipitation in the basin during the 1970s (Yang et al., 2004).
Despite continued construction of reservoirs in the basin, their flood detention capacity remains limited. Therefore, peak flow remains high following heavy rainfall. However, water and soil conservation measures implemented during change period I in the Qinhe River Basin have yielded positive results. The completed reservoir has effectively reduced peak flood volume, resulting in a decreasing trend in flood peak and three-day flood volume data. In change period II, the water and soil conservation measures, including water conservancy projects, in the basin impacted flood detention and peak cutting. Furthermore, precipitation in the basin decreased during the same period, leading to a further decrease in the three-day flood volume and peak flow. These results demonstrate that the construction of reservoirs has significantly enhanced the prevention of water-related disasters in the basin.