In the middle reaches of the YRB, soil conservation practices, including biological measures (e.g., trees and pasture) and structural projects (e.g., terraces and dams), were implemented in the 1970s and 1980s because of severe soil losses that contributed to >90% of the total river sediment load. Thus, the DMC exhibits breakpoints in 1970 and 1990 (Figure 10). The effects of human activities on runoff increased gradually, reaching 80.36% and 80.63% in the two affected periods. As shown in Table 7, the soil conservation area has expanded with time. Human activities have changed the local micro-topography, increased the ability of intercepting precipitation, and consequently, delayed and reduced the runoff (Miao et al. 2011). Tang indicated that the surface runoff decrease in the upper and middle reaches due to soil conservation measures was approximately 0.63 × 10⁹ m³/year over the period of 1980–1997 (Tang 2004). In addition, the Sanmenxia reservoir, the first large reservoir built in the river basin, is located in the middle reaches (Figure 1). The Xiaolangdi reservoir, which has a storage capacity of 12.7 km³ and a 160 m high dam wall, is also located in the middle reaches between the Sanmenxia reservoir and Huayuankou station. In 2002, the YRCC initiated the Water-Sediment Regulation Scheme, which uses the controlled release of floodwaters from the Xiaolangdi reservoir and other small reservoirs to distribute the sediment retained within the Xiaolangdi across the lower reaches (Wang et al. 2005). These major reservoirs are situated on the main stream, and make the largest contributions to water regulation and sediment retention (Wang et al. 2006).