中文摘要：

针对中国北方干旱半干旱缺水地区高含沙河流汛期洪水资源难于控制利用及评价的问题,以径流特征及水资源开发利用均具有典型性的泾河为例,根据河流径流特征和水资源利用特点,利用流域1933年-2001年汛期6月-10月的径流量、径流泥沙含量和引水量资料,基于它们之间的内在联系,把基本资料序列从小到大进行排列并划分成若干等级,通过对各等级的统计获得上三角形形式的洪水弃水系数与其影响要素之间的等级关系,提出汛期洪水弃水系数计算的分级最大值法,可快速准确地确定出不同沙限下的汛期洪水弃水量,通过与传统方法的比较,结果表明本研究提出的分级最大值法计算所得结果更为合理有效,为流域洪水资源的开发利用及评价提供一种行之有效的方法。

英文摘要：

Due to the existence of severe soil and water losses over arid,semi-arid and water-shortage areas in North China,the phenomenon of high sediment concentration in runoffs would occur.The floodwaters in flood season are however difficult to be controlled and utilized,which results in floodwater waste in flood season and an intense situation of water resources supply and demand.This study makes an attempt to seek a relatively optimal approach to evaluating the abandoned floodwater in flood period,that is,the flood volume in flood season that cannot be controlled and utilized by engineering measures.A case study on the Jinghe River,one branch of the Weihe River and a second tributary of the Yellow River,China,was carried out.Both the runoff characteristics and the water resources development and utilization of the Jinghe River basin were taken into account.In terms of the characteristics of runoff and water resources development and utilization in the river basin,three data sequences regarding runoff,sediment concentration in runoff and water diversion amount from the river to the Jinghuiqu Irrigation District in the lower reaches were employed.The data were measured monthly from June to October for the period of time 1933-2001 at the control section of the Jinghuiqu Irrigation District.Their inherent relationships were analyzed in detail.The sequential data about the ratio of water diversion of runoff and the sediment concentration in runoff were generally divided into several grades in an ascending order.The months of their occurrence at each grade were recorded.A rating relationship between the coefficient of abandoned floodwater in flood season and the corresponding influencing factors （e.g.,the sediment concentration in runoff） was obtained in the left upper triangular form.A maximum rating method for coefficient determination of abandoned floodwater in flood season was then presented.The product of the coefficient of abandoned flood water and the natural runoff in flood season can be taken as the volume of