黄土区小流域植被/工程复合作用下的泥沙效应

研究植被/工程复合作用下的泥沙效应,为科学阐述黄土区不同水土保持措施耦合作用下的调水调沙效益提供参考依据。马家沟流域土地利用主要分为草地、林地、梯田、坡耕地、灌木林地、裸地、居民地和水域8类,流域布设各类淤地坝64座。基于SWAT模型,对比分析了多林流域和少林流域对流域泥沙的调节作用,分析了淤地坝淤积库容、单坝拦沙效益,研究了流域各项水土保持措施减沙效益。研究结果表明,森林植被除了缓洪增枯,同时可以减少流域侵蚀产沙,农果地与全林流域相比,输沙模数为后者的1.5倍;淤地坝坝控面积与坝高、库容与坝高均正相关,相关系数分别为R2=0.8121、0.8603。黄土区流域植被/工程复合作用下水土保持效果显著,而在各项水土保持措施中,淤地坝减沙贡献率最大,达40%以上。

Vegetation Combined with Engineering Controls for Sediment Reduction on the Loess Plateau

Adequate vegetation and engineering measures are important for soil and water conservation in loess areas. We investigated the sediment reduction achieved when various degrees of vegetative cover were combined with a silt dam in the Majiagou watershed, a typical watershed on the loess plateau. The effectiveness of various soil and water conservation measures were evaluated by comparing paired subsheds with different degrees of forest cover. Sediment yields, sediment reduction by a single dam, and storage capacity of silt dams were compared based on results from the SWAT (Soil and Water Assessment Tool) model. The study provides a reference on the effectiveness of different soil and water conservation measures on the loess plateau. Eight landuse types were identified in Majiagou watershed; grassland, forest, terraced cropland, sloping cropland, shrub land, unvegetated, residential and water. A total of 64 silt dams are distributed in the watershed. To analyze the soil protection provided by different types of vegetation, two pairs of subsheds were selected with similar terrain and landform factors (No. 12 and No. 18, No. 27 and No. 31) and sediment transport from the paired subsheds was compared. Land use in subshed No.12 is dominated by woodland and sloping cropland, with vegetation coverage of 80.1%, while land use in subshed No.18 is dominated by degraded grassland and sloping cropland, with vegetation coverage of 12.4%. Land use in subshed No.27 is dominated by farmland, fruit orchards and grassland, with vegetation coverage of 8.1%, while subshed No.31 is a forested watershed, with natural secondary forest cover of 94.4% and artificial forest cover of 5.6%. The sediment transport modulus of subshed No. 18 was 1.57 times higher than that of No. 12, with rainfall of 330.9 mm, and 1.52 times higher with rainfall of 515.2 mm. The sediment transport modulus of subshed No. 27 was 1.55 times higher than that of No. 3, with rainfall of 330.9 mm, and 1.45 times higher with rainfall of 515.2 mm. Results indicate that forest vegetation significantly reduces flooding, soil erosion and sediment yield in the watershed. Both the land area served and the storage capacity of silt dams increased exponentially with dam height (R2 = 0.8121 and 0.8603, respectively). Effective soil and water conservation is achieved on the loess plateau when adequate vegetation is combined with engineering controls. Among the various conservation measures employed in the Majiagou watershed, silt dams most effectively reduce sedimentation, contributing >40%.