中文摘要：

宁蒙黄河河段主要穿行于断陷盆地中,近期淤积严重,同流量洪水水位抬升,洪灾和土地盐碱化问题加重。为了弄清该河段泥沙淤积长期变化过程,正确预测河段泥沙淤积变化趋势,以利制定合理的治河措施,本文利用河段来水来沙与河道淤积关系、气候要素与区域产沙关系以及古气候与古径流等相关资料,重建了宁蒙河段近500多年来年沉积量的变化过程。结果显示1989年以前505年间宁蒙河道年均泥沙沉积量达0.55×10^8 t/a,其中1850年至1989年间为0.52×10^8 t/a,高于上世纪50至80年代宁蒙河道年均泥沙沉积量。因此黄河宁蒙河段是一个长期泥沙淤积比较强烈的河段。虽然近20多年来宁蒙河段年淤积量已高于近500多年来宁蒙河道年泥沙沉积量,但历史上也出现过连续25年河道年均淤积量接近近20多年的年均淤积量。

英文摘要：

The Yellow River flows in a series of subsiding graben basins in its Ning-Meng reach.In recent years,channel aggradation in the Ning-Meng reach aggravated,leading to the rise of water level at the same water discharge and the exacerbation of flood hazards and soil salinization /alkalization.In order to clarify the long-term changes in sediment accumulation in the reach,which is necessary for making better prediction of its tendency and forming rational measures of river management,this study reconstructed the process of changes in annual sediment accumulation in the Ning-Meng reach in the past over 500 years.The estimate of the annual sediment accumulation was based on the relationships between the sediment accumulation and water and sediment inputs to the river reach and between sediment yield in the tributaries in the river reach and climatic factors,data of climate of the surrounding region and runoff of the river in the study period,and others.The results show that the mean annual sediment accumulation in the Ning-Meng reach was about 55 × 10^6t /a in 505 years before 1989 and 52 × 10^6t /a in 140 years in the period from 1850 to 1989,which was 5 times of the average in the whole Quaternary period and also higher than that in the period of 1950s to 1980s.This size of sediment accumulation suggests that the Ning-Meng reach has been subjected to intensive aggradation for a long term.Although the mean rate of sediment accumulation in the Ning-Meng reach in recent over 20 years surpassed that in over 500 years before then,some 25-year means close to the average in recent over 20 years did occur in the past over 500 years.