风力侵蚀对无定河流域产沙作用定量分析

本文利用无定河的水文泥沙观测日值资料和该流域内及周围气象站气象观测月值资料,通过流域的水沙关系与各年风蚀气候因子,估计了风力作用对无定河流域产沙的贡献量。结果揭示出:在风沙区,由于水力的搬运作用仍然决定了流域输沙量的大小,所以风力作用产生的输沙模数很小,在总输沙量中只占约1/4;风力作用增加输沙量比例最大的地区是穿过风沙区和丘陵沟壑区交界区,既有活跃的风沙活动又有强烈的黄土水蚀,风力和水力形成强耦合侵蚀搬运作用的干流上游,占输沙量的1/3以上;位于靠近风沙区并有片沙分布的黄土丘陵沟壑区的流域,风蚀产沙占流域输沙量的比例约为1/10;在黄土丘陵沟壑区,相对强烈的水力侵蚀,风力作用对产沙影响较小。整个无定河流域风力作用产生的输沙量包括入河风沙、降尘以及风力与水力的耦合侵蚀搬运作用可能增加的泥沙,接近流域总输沙量的1/6。

A quantitative analysis of the effects of wind erosion on sediment yield in the Wudinghe River watershed

The Wudinghe River watershed is located in the transitional zone between the hilly and gully area of the Loess Plateau and the Mu Us desert,and is a principal contributor of sediment to the Yellow River.Both water erosion and wind erosion are responsible for the heavy sediment yield from the watershed.The contribution of wind erosion to the sediment yield of the watershed is estimated using water-sediment relationships based on water and sediment discharge records at hydrological stations in the watershed and a wind erosion climatic factor calculated from meteorological measurements recorded at meteorological stations in and around the watershed.The results reveal that the role of wind erosion in sediment yield was different in areas with different surface materials during the period from 1958 to 1970 when the water-sediment relationships in the watershed had not been noticeably interfered by practices of water and soil conservation.In the areas with loess hills and gullies water erosion was intensive,and a comparatively low proportion of sediment yield was related with wind erosion.The proportion of wind erosion derived sediment yield of a tributary draining the northern margin of the loess hills and gullies which is near the deserts and covered with sporadic patches of sands was also below 10%.In desert,sediment transport by water played a main role in sediment yield,and the sediment yield associated with wind erosion was only about 1/4 of the total for a tributary draining this area.The highest proportion,over 1/3,of sediment yield due to wind erosion occurred in the area where the river flows between sands and loess areas.The coexistence of both intensive wind erosion in the sands and strong water erosion in the loess areas results in the best collaboration of water and wind in eroding and transporting sediment.For the whole Wudinghe watershed,wind erosion increased by about 1/6 of the total sediment yield through transporting sand and dust from deserts to the river and through promoting water erosion.