黄河河龙区间退耕还林前后淤地坝拦沙特征分析

为探究黄河中游河龙区间退耕还林工程实施前后淤地坝拦沙变化特征,采用实地测量和文献集成分析相结合的方法,分析了退耕前后多个时段河龙区间不同分区淤地坝的拦沙特征。结果表明:退耕后,河龙区间北部、中部和南部淤地坝平均拦沙模数分别为7138.5 t km~(-2) a~(-1)、2596.5 t km~(-2) a~(-1)和4230.9 t km~(-2) a~(-1),比退耕前分别减少了49.5%、84.1%和52.1%,且均显著小于退耕前,坝控流域侵蚀程度总体上由极强烈侵蚀、剧烈侵蚀和极强烈侵蚀分别转变为强烈侵蚀、中度侵蚀和中度侵蚀;退耕前河龙区间中部和南部淤地坝拦沙模数随时间推进显著降低;退耕后河龙区间北部淤地坝拦沙模数随时间推进而下降。未来河龙区间淤地坝建设应根据小流域侵蚀产沙现状适当缩减规模,以免造成水土资源浪费,影响下游的用水安全。

Characteristics of sediment retention by check-dams before and after the "Grain for Green" project in the He-Long Reach of the Yellow River

The Hekouzhen-Longmen Reach (He-Long Reach) in the middle of the Yellow River is the primary source area of sediment of the Yellow River. Check-dams are a widely used measure for controlling soil and water losses in this area. To explore the response of sediment retention by check-dams to the "Grain for Green" project in the He-Long Reach, the authors investigated the sediment deposition of eleven check dams and collected the data of sediment yield from another twenty-nine check dams using literature integration. The results indicated that the average annual dam-trapped sediment yields in the northern, middle, and southern region of the He-Long Reach all tended to decline over time and were drastically different between different periods. After the "Grain for Green" project, the average annual dam-trapped sediment yields in the northern, middle, and southern region of the He-Long Reach were 7138.5 t km^-2 a^-1, 2596.5 t km^-2 a^-1, and 4230.9 t km^-2 a^-1, respectively, which decreased by 49.5%, 84.1%, and 52.1% compared to those before the project, respectively. Furthermore, the average annual dam-trapped sediment yields in different regions of the He-Long Reach were all significantly less than those before the "Grain for Green" project. The overall soil erosion severity on dam-controlled watersheds in the northern, middle, and southern region of the Reach turned into high, moderate, and moderate from very high, severe, and very high, respectively. Before the "Grain for Green" project, the average annual dam-trapped sediment yields in the middle and southern regions of the He-Long Reach both declined over time, being drastically different between different periods. Among the three sub-zones in the Reach, the effects of the "Grain for Green" project on reducing sediment yield increased in the following order:the northern region < the southern region < the middle region. This research demonstrates that the "Grain for Green" project and erosion control practices can both effectively reduce erosion sediment yield of small watersheds. In future, the construction of check-dams in the He-Long Reach of the Yellow River should be appropriately reduced to save soil and water resources and guarantee water security downstream.