中文摘要：

黄河宁蒙河段的水文和水温过程近几十年来发生了显著变化,迫切需要评估这一变化对河道形态、凌汛的影响及其可能的致灾效应。利用同水位河道过水断面形态参数分析方法,选取宁蒙河段稳定封冻区域（石嘴山-头道拐）的石嘴山、磴口、巴彦高勒、三湖河口和头道拐5个主要水文站,根据2008-2013年凌汛前实测断面资料,计算相应年份5个水文站同水位下的河道断面面积、平均水深和深泓点高程。结果表明,宁蒙河段近年来凌汛期的径流量和水温呈现逐渐增大的趋势,下泄流量过程有助于减少凌灾发生的几率;各水文站凌汛前的断面面积和平均水深等断面形态参数呈逐年增大的趋势,深泓点高程不断降低。河道过水断面形态的这种变化增大了凌汛期河道的过流能力,有助于缓解开河期可能出现的凌汛灾情。

英文摘要：

The hydrological process and water temperature process have changed markedly during the flood season in the Ningxia- Inner Mongolia reach of the Yellow River in recent decades.Assessing the impact on river channel geometry,ice floods and the possible disaster- causing effects are needed Based on cross- sectional data measured before each ice flood season at Shizuishan,Dengkou,Bayangaole,Sanhuhekou and Toudaoguai gauging stations located in the stable frozen section of the Ningxia- Inner Mongolia reach from 2008 to 2013,we selected the lowest water level for each station as the given water level to calculate geometrical parameters under a given water level. To reveal geometrical changes in cross section effectively,we selected channel cross-section area,mean water depth and elevation of thalweg in order to analyze changes.We found that runoff and mean water temperature during each flood season increased from 2008 to 2013 in the Ningxia- Inner Mongolia reach of the Yellow River. The discharge process of the Qingtongxia Reservoir in each ice flood season accorded with ideal discharge processes and thus contributed to a reduction in ice flood disasters. The cross- section area and mean water depth before each ice flood season showed an increasing trend year by year at the five main gauging stations,while the elevation of thalweg dropped comparatively. These changes in channel geometry caused the enhancement of flow capacity,helpful for relieving possible disasters during thawing periods.