Spatiotemporal variation of wind erosion intensity in region of Ten Small Tributaries in Inner Monglia branch of Yellow River

Abstract: 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, 7.03×10-3 and 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.