黄河内蒙古支流“十大孔兑”区风蚀强度时空变化特征

摘要

Wind erosion is widespread in arid and semiarid regions around the world and it has been considered as a serious environmental threat that leads to change in global biochemical cycles, decline in agricultural productivity, and contributes to climate change. Aeolian erosion provides abundant eroded sediments for channel sediments delivery in the ten small tributaries. In order to reveal the mechnism of wind erosion in the region of ten small tributaries, three plots were established in Dongliugou watershed of the ten small tributaries in Inner Mongolia. The first monitoring plot (40°18′28″N, 110°30′57″E) was located in the criss-cross region of farmland and moving dune, the second monitoring plot (40°09′52″ N, 110°28′5″ E) was located in moving dune and the third monitoring plot (40°04′19″ N, 110°28′17″ E) was located in the criss-cross region of fixed and moving dune. The amounts of wind erosion and the change of surface shape were monitored by the method of pins measurement for 1 year. Combining the local meteorological data with the monitoring data, spatial and temporal variation of wind erosion intensity was analyzed by using the technologies of ArcGIS and Surface 8.0. The results showed that: 1) The average intensity of wind erosion from the plots during the months from April to May in 2014 were 11.54×10-3, 21.11×10-3, and 9.35×10-3 kg/(m2·d), respectively, and that from October to November in 2013 were 2.96×10-3, 7.03×10-3and 2.29×10-3 kg/(m2·d), respectively. The intensity of wind erosion from April to May was 2-3 times stronger than the annual average intensity. The intensity of wind erosion was exponentially related with the maximum wind velocity in the study area. Based on the temporal variation of cumulative wind erosion of the monitoring plots, the proportion of sediments into Yellow River through wind erosion was 60.44% (spring)> 18.22% (autumn)> 15.75% (summer)> 5.59% (winter) in the region of ten small tributaries; 2) The wind erosion modulus of 3 monitoring plots were 1149.75, 1821.35 and 3164.55 t/(km2·a), respectively. The contents of erodible particles was 94.95% (midstream)> 62.18% (upstream)> 44.51% (downstream), thus the amounts of wind erosion of middle reaches (216.71 kg) were significantly higher than upper reaches (78.81 kg) and downstream (124.76 kg) in the region of ten small tributaries. In this study, the amounts of wind erosion of downstream were significantly higher than upstream although the contents of erodible particles in upper reaches were more than downstream. It was caused by land use patterns and human disturbance; 3) The area of Kubuqi desert was moderate wind erosion, the region of Loess hilly and gully and the South Bank of the Yellow River alluvial plain area were mild wind erosion. It’s estimated that the three surface cumulative amounts of wind erosion were 8.74, 5.95 and 5.16 Mt, the proportion of sand blown by the wind into the Yellow were account for 44.03%, 29.97% and 26.00%; 4) The main direction of wind erosion was from northwest to southeast, and the process of wind erosion was accumulation, erosion, passage, and then deposition. The surface amplitude of midstream was significantly increased from April to May and form October to November, but hardly changed in the other months. Surface amplitude was linearly correlated with intensity of wind erosion (R2=0.78,P<0.05). Wind erosion has the ability to restore surface. The study may provide evidences for preventing increasing sediments for the river channel from the region of the ten small tributaries and to formulate reasonable soil and water conservation measures.%十大孔兑的风蚀作用过程为河道输沙提供了重要的泥沙来源。为揭示十大孔兑风蚀作用规律，选取3种典型下垫面建立风蚀监测小区，利用侵蚀针法对研究区风蚀量及地表形态进行了为期1 a的实地监测。在此基础上，综合当地气象资料，分析研究区风蚀强度及地表形态变化规律，结果表明：1）研究区风蚀强度与平均极大风速呈指数关系，10－11月和4－5月风蚀强度大于全年其他时间，4－5月风蚀强度最大，是全年平均风蚀强度的2～3倍；2）土壤可蚀性颗粒含量大小分别为库布齐沙漠区（94.95%）>黄土丘陵沟壑区（62.18%）>黄河南岸冲积平原区（44.51%）。库布齐沙漠区属于中度风蚀，黄土丘陵沟壑区和黄河南岸冲积平原区属于轻度风蚀，十大孔兑3种地形年累积风蚀量估算结果分别为8.74、5.95和5.16 Mt，风沙入黄所占总量比例分别为44.03%、29.97%和26.00%；3）研究区风蚀发生的方向主要为东南方向，监测小区的风蚀过程主要为堆积-吹蚀-推移-再堆积，地表起伏度随风蚀强度增加呈线性增加趋势（R2=0.78，P<0.05）。研究结果可为防治十大孔兑泥沙淤积与合理配置水土保持措施提供科学依据。