黄河主要产沙区近年降雨及下垫面变化对入黄沙量的影响

近几年,黄河来沙量锐减原因成为人们普遍关注的热点问题。本文以天然产沙量约占流域入黄沙量90%的黄河潼关以上主要产沙区为研究范围,优选了降雨因子和模型的函数型式,改进或构建了各支流在天然时期的降雨~产沙相关模型,进而分析了该区近35年不同时段的降雨和下垫面因素的减沙作用。研究表明,若以各支流1956—1975年前后的降雨-产沙响应关系为基准,1980年以来下垫面减沙作用越来越大,近十多年最为突出。近10年研究区降雨总体偏丰、其中近5年明显偏丰,因此降雨变化不是黄河该时段来沙锐减的原因;2005—2014年和2010—2014年,下垫面因素的实际总减沙量分别为13.87~15.45亿t/a和15.70~18.70亿t/a。

Effects of rainfall and underlying surface on sediment yield in the main sediment-yielding area of the Yellow River

Sediment yield of the Yellow River has obviously decreased in recent years, which had become a hot topic of general interest. In this study,basin area above Tongguan station was choose as the study re-gion which natural sediment yield accounted for about 90% of the total sediment yield in the entire Yellow River basin. The rainfall-sediment correlation models was modified with the optimized rainfall indexes and model''s function type, and then sediment reduction effects of both rainfall and underlying surface factors were analyzed by using the correlation models. The results show that the sediment reduction effect of the underlying surface has been getting larger and larger since 1980, especially in recent 10 years, taking the rainfall-sediment correlation of each branches during 1956 to 1975 as a benchmark. In recent 10 years, the rainfall was generally more plentiful than the average value of it in 1956-2014,and so the rainfall fac-tor was not the reason of the sediment yield reduction of the Yellow River. The total sediment reductions due to the change of the underlying surface in 2005-2014 and 2010-2014 were separately 1387~1545 mil-lion t/a and 1570~1870million t/a.