Water and sediment changes at important sections of the main and tributary streams of the Yellow River (eastern and central Gansu Province, China) over the past 68 years

The Longdong and Longzhong regions, located upstream of the Yellow River Basin in the arid inland area of Northwest China, are also situated on the western part of the Loess Plateau. Water and sediment changes are important indicators of regional changes in water and soil resources. After dividing the Longdong and Longzhong areas of the Yellow River Basin, this study analyzes the runoff and sediment transport data in 14 key hydrological sections along the main and tributary streams of the three areas from 1956 to 2023. To understand the interannual variation trends, mutation points, and periodicity of the regional water and sediment, the long-term runoff and sediment changes were characterized through a time series analysis, a Mann-Kendall trend analysis, a Pettitt mutation point test, and continuous wavelet transform methods. The results indicate (1) downward trends in water and sediment in the main hydrological monitoring sections from 1956 to 2023, with sediment transport declining more significantly than water transport; (2) the Zuli River, Wei River, and Jing River, which are low in water and enriched in sediment, should be prioritized for soil erosion control; (3) most mutations in the water and sediment series at each section occurred in the 1980s and 2000s. The main periodicity of runoff was 10 years while the main periodicity of sediment transport varied. In conclusion, the water and sediment in both the main and tributary streams of Yellow River in the Longdong and Longzhong regions have trended downward since the 1950s. The annual runoffs in the main stream and a small number of tributaries of Yellow River have rebounded, indicating the effectiveness of water and sediment control over the past 68 years.