Abstract. To control severe soil erosion on the Loess Plateau, China, a great number of soil conservation measures have been adopted since 1950s and subsequently, the "Grain for Green" project has been implemented from 1999. The measures and the project result in a large scale land use/cover change (LUCC). Understanding the impacts of the measures and the project on streamflow, sediment load and their dynamic relation is essential as the three elements are closely related to the sustainable catchment management strategy on the Loess Plateau. The data for seven selected catchments in the middle reaches of the Yellow River were used and standardized with precipitation and the controlling area for analysis. Nonparametric Mann-Kendall test and Pettitt test were employed to detect trends and change points of the annual streamflow and annual sediment load. Simple linear regressions for the monthly streamflow and sediment load from May to October were made to express their dynamic relation. Based on the change point identification and the time when the project began to implement on the Loess Plateau, the whole time for the data records was divided into three periods to compare the change extents in streamflow, sediment load and their dynamic relation between catchments. Results show that there are three types of responses in streamflow, sediment load, and their dynamic relations for the seven catchments. The effects of the LUCC on streamflow, sediment load, and their dynamic relation are greatest in the three transition zone catchments with the two rocky mountain catchments followed. The effects are much weaker in the two loess hilly-gully catchments. In general, the change extents for sediment load are much greater than those for streamflow, which results in the increasingly weakening trends of statistical significance for the dynamic relation between the periods.
Trends of streamflow, sediment load and their dynamic relations for the catchments in the middle reaches of the Yellow River in the past five decades