无定河粗泥沙产沙量的变化及其原因

Temporal variation of the coarse sediment yield in the Wudinghe River Basin and the cause of formation

为了解决黄河治理中迫切需要解决的粗泥沙来源和数量问题,依据大量实测资料,运用统计方法对无定河粗泥沙产沙量进行研究。结果表明:无定河流域d>0.05 mm粗泥沙产沙量呈现出减少趋势,这种减少与年降水量、年沙尘暴频率的减少和水土保持面积的增大有一定的因果关系;估算出最大30 d降雨量和年沙尘暴频率的变化对d>0.05 mm粗泥沙产沙量变化的贡献率分别为66.5%和33.5%,即沙尘暴特征的变化对粗泥沙产沙量变化的贡献率相当于暴雨特征的变化贡献率的1/2。建立了粗泥沙年产沙量与最大30 d降雨量、年沙尘暴频率和水土保持措施面积之间的回归方程,表明粗泥沙年产沙量随最大30 d降雨量、年沙尘暴频率的减小而减小,随水土保持面积的增大而减小。因此,20世纪50年代以来暴雨的减弱、沙尘暴的减弱和水土保持措施面积的增大是无定河流域粗泥沙产沙量减少的原因。

Based on the data of suspended sediment yield, suspended sediment grain size, precipitation, sand-dust storms and areas of soil and water conservation measures, a study has been made on the relatively coarse （〉 0.05 mm） sediment yield （Qs, 〉0.05） in the Wudinghe River. The Qs, 〉0.05 shows a decreasing trend, which can be related with the decrease in annual precipitation （Pro） and number of sand-dust storm days （Dss） and the increased area of soil and water conservation measures （Atfgc）. To assess the influence of precipitation and sand-dust storm on Qs, 〉0.05, a number of two-variable regression equations has been established, which Qs, 〉o.o5 relates to Das and one of the four rainfall indices： annual precipitation （Pm）, highflow season （June - September） （ P6-9）, annually 1 day maximum （ PI ） and maximum 30 day （P30） precipi- tations. It has been found that the multiple correlation coefficient of the equation involved Qa, 〉 0.05 and Das and P30 is the largest, and the contribution of Dsa and P3o to In Qs, 〉0.05 was estimated as 66.5% and 33.5%. A multiple regression equation between In Qs, 〉0.05 and three influencing variables （Dss, P30 and Atfgc） has been established, which indicates that the 〉 0.05 mm sediment yield increased with Dss and P30, but decreased with Atfgc. Thus, the decrease in precipitation and sand-dust storms and the increase in the area of soil and water consrvation measures are the cause for the decreasing trend in the relatively coarse sediment yield.