渭河下游干流堤防防洪能力分析

三门峡水库修建后,由于泥沙淤积严重,渭河下游防洪问题突出.本文根据实际资料,对渭河下游大堤各段防洪能力进行了分析,并提出了一些建议.     

对渭河防洪问题的思考

渭河的防洪问题,是陕西省沿渭各级政府、社会各界日益关注的重点和焦点之一。通过对渭河存在的泥沙淤积严重、工程防洪能力低、支流问题突出、小水大灾频繁等问题进行深入分析思考,提出从控制洪水向管理洪水转变,加快渭河防洪工程体现建设、突出解决南山支流防洪问题、综合解决渭河下游泥沙淤积问题。坚持工程措施与非工程措施相结合,不断加强基础研究、防汛预警及指挥信息系统等非工程措施建设,依法科学防洪,最大限度减少灾害损失。     

渭河下游泥沙淤积原因及减淤措施

三门峡建库以来,渭河下游泥沙淤积严重,分析其原因,主要受水沙条件和潼关高程的影响.针对渭河下游的泥沙问题,本文提出了在上游干支流上修建水库,进行调水调沙;在下游降低潼关高程,有利于渭河下游的水沙排泄的基本对策.     

渭河下游近期冲淤情势分析

渭河下游是陕西省重点防汛地区之一,因此,渭河下游的冲淤情况直接关系到陕西省关中东部的社会经济发展和沿河群众的生命财产安全的大问题。本文分析了21世纪以来渭河下游的冲淤情势,总体来讲渭河下游河道产生冲刷,并重点分析了河道冲刷的原因,以为渭河下游的防洪和治理提供科学的依据。     

渭河下游临渭区河段砂石资源可开采量分析

通过分析渭河下游临渭区河段砂石资源贮量、补给量的分析,利用有关研究成果计算临渭区河段主槽机械抽砂采砂坑的允许开采深度与允许开采长度,结合规划开采区域计算了临渭区砂石资源可开采量约130.9万m3,提出在实际采砂管理中应加强的措施建议。     

潼关高程的变化及其对渭河下游洪水的影响探讨

三门峡水库1960年投入使用之后,经过两次改建和三次运行方式调整,不仅发挥了较大的防洪效益,也为多沙河流上修建水库长期保持兴利库容积累了丰富经验。但水库运用也给库区造成一系列问题。通过分析潼关高程的变化及其对渭河下游河道及下游洪水特征值的影响,提出了防治渭河下游洪灾的对策。     

依托库区治理工程促进"数字渭河"建设

陕西三门峡建库以来,渭河下游灾害额发.近年来通过渭河下游治理工程的建设实施,减轻、减缓了洪涝渍、盐碱灾害.随着计算机技术的发展,"数字流域"的探讨和开发建设已逐步提上日程,目前"数字黄河"工程已经启动,"数字渭河"的建设势在必行.通过分析,提出渭河治理的发展方向是要依托工程建设,利用现代化信息技术,从建设渭河"数字防汛"开始,逐步实现"数字渭河"基本功能.     

21世纪黄河下游防洪减灾对策

黄河是受人类活动强烈影响的河流,随着人类活动对流域环境的影响日趋增强,进入黄河下游的水沙条件发生了重大改变,防洪出现了许多新情况、新问题。黄河水资源进一步开发利用,下游牵断流及小水时间逐年延长,黄河将无有效输沙水量,如果来沙不能控制,现行河道的行洪能力和寿命将始终是中国的忧患。小浪底水库２００１年投入运用后,对黄河下游又将强烈堆积。２１世纪社会经济发展对黄河下游防洪减灾提出了更高要求,根据多年对黄     

太湖流域应对特大洪水防洪工程效益模拟

防洪效益评估对防洪工程投资决策与减灾对策制定具有重要意义。建立集成了与太湖流域防洪效益评估相关的系列模型和方法,包括含降雨产流与平原净雨计算的水文分析方法、由河网水动力学模型和平原区域洪水分析模型组成的大尺度水力学模型、综合流域社会经济和淹没因素的洪灾损失评估模型。模拟了太湖流域遇特大洪水的灾害损失,开展了不同防洪工程应对流域性特大洪水减灾效益的预测分析。结果表明:1999年型200年一遇降雨将会给太湖流域造成高达568.29亿元的直接经济损失,外排动力增强30%至100%的防洪效益介于26.69亿元到45.70亿元之间,新建圩区、太浦河拓宽的防洪效益依次减小,而圩区泵排能力增加30%的防洪效益仅为0.65亿元。基于研究成果提出了增设外排泵站、加强圩区科学调度、通过保险分担风险等应对特大洪水的对策措施建议,为太湖流域特大洪水的防治提供支撑和参考。     

太湖流域应对特大洪水防洪工程效益模拟

防洪效益评估对防洪工程投资决策与减灾对策制定具有重要意义。建立集成了与太湖流域防洪效益评估相关的系列模型和方法,包括含降雨产流与平原净雨计算的水文分析方法、由河网水动力学模型和平原区域洪水分析模型组成的大尺度水力学模型、综合流域社会经济和淹没因素的洪灾损失评估模型。模拟了太湖流域遇特大洪水的灾害损失,开展了不同防洪工程应对流域性特大洪水减灾效益的预测分析。结果表明：1999年型200年一遇降雨将会给太湖流域造成高达568.29亿元的直接经济损失,外排动力增强30%至100%的防洪效益介于26.69亿元到45.70亿元之间,新建圩区、太浦河拓宽的防洪效益依次减小,而圩区泵排能力增加30%的防洪效益仅为0.65亿元。基于研究成果提出了增设外排泵站、加强圩区科学调度、通过保险分担风险等应对特大洪水的对策措施建议,为太湖流域特大洪水的防治提供支撑和参考。     

井点降水实验在渭河大桥承台施工中的应用

井点降水是一种方便易行的降水方式,在黄河湿地承台施工中较好地解决了基坑开挖基坑涌水、流沙现象的发生。     

崩塌滑坡防治施工监测与治理效果

论文较系统地介绍了崩塌滑坡地质灾害防治施工安全监测和防治效果监测的目的和特点、监测方案布置原则,监测内容与监测方法等。指出防治施工安全监测和防治效果监测是整个监测过程的两个不同阶段。其监测方案布置应当统筹规划,区别对待。还以2个工程实例进行了阐述和分析,对开展崩塌滑坡防治阶段的监测工作有较强的实用价值。最后,作者强调监测工作应贯穿于防治工程的始终。     

Effect of saltwater intrusion on groundwater environment in Weihe River downstream,Shandong Province,China

Based on the geological and hydrogeological conditions along with dynamic changes of groundwater level, this paper analyzes the hydrodynamic characteristics of saltwater intrusion in the study area. According to monitoring data of groundwater quality, the distribution characteristics of macro component are analyzed, and then fuzzy comprehensive evaluation method is adopted to evaluate the impact of saltwater intrusion on groundwater environment. Concerning the influence degree of groundwater environment, the study area is divided into brine area, seriously influenced area, moderately influenced zone, slightly influenced zone and uninfluenced zone. The results can offer references for prevention and control of saltwater intrusion as well as the protection of water resources.     

Effect of saltwater intrusion on groundwater environment in Weihe River downstream,Shandong Province,China

Based on the geological and hydrogeological conditions along with dynamic changes of groundwater level,this paper analyzes the hydrodynamic characteristics of saltwater intrusion in the study area.According to monitoring data of groundwater quality,the distribution characteristics of macro component are analyzed,and then fuzzy comprehensive evaluation method is adopted to evaluate the impact of saltwater intrusion on groundwater environment.Concerning the influence degree of groundwater environment,the study area is divided into brine area,seriously influenced area,moderately influenced zone,slightly influenced zone and uninfluenced zone.The results can offer references for prevention and control of saltwater intrusion as well as the protection of water resources.     

The ecological effects of structural flood mitigation works on fish habitats and fish communities in the lower Clarence River system of South-Eastern Australia

The effects of flood mitigation structures on the quality of estuarine and freshwater fish habitats in the lower Clarence River system of south-eastern Australia were investigated. Surrounding land use, fringing vegetation, overall level of habitat disturbance, distance from the sea, salinity, and water temperature were examined and compared between four sites on natural tributary streams, four sites on channelized flood mitigation drains gated at their mouths, and ten paired sites (five below and five above floodgates) on flood mitigation drains in this system, from mid 1988 to late 1990. Quantitative sampling of the fish fauna at each of these sites was conducted quarterly over this 21/2-yr period. Juvenile fishes were sampled using netting enclosures together with application of the ichthyocide rotenone, while subadults and adults were sampled using multiple-panel gill nets. In general, fish habitats in the flood mitigation drains, and especially those above flood gates, had more intensive surrounding land uses, less natural native fringing vegetation and, overall, were more highly disturbed than those in the natural tributaries. Salinity at the various study sites was largely dependent on the pattern of seasonal (mainly summer and autumn) rainfall and distance upstream from the sea. Salinities usually differed only slightly between gated and ungated sites at similar distances from the sea, indicating that the floodgates were generally ineffective in preventing the penetration of saline river water into the drains immediately above them. These gates were, however, very effective in preventing the establishment of fringing mangrove vegetation in the drains above them. The main ecological effects of these flood mitigation works have thus been to generally degrade the overall quality of available fish habitat, particularly in terms of reductions in natural fringing vegetation (mangroves in the more estuarine-dominated areas and overhanging terrestrial trees in the more freshwater-dominated areas often being replaced by grassess and rushes), and to increase the intensity of surrounding land use (natural forest often being cleared and wetlands drained for cattle grazing and sugarcane growing), both of these factors contributing to increases in generalized aquatic habitat disturbance. Results from the study of the fish assemblages in these natural and man-altered habitats revealed the following general patterns. Highest fish species numbers and abundances occurred in the ungated natural tributaries and in drains downstream of floodgates. These habitats also contained the largest proportions of both commercial fish species and individuals as well as the majority of species and individuals with marine-estuarine affinities. Both total and commercial fish species numbers generally declined with decreasing salinity and increasing distance of the sampling sites from the sea. Even through saline waters from the main river system penetrated the majority of the floodgates during most of the study period, fish passage through these gates was found to be very restricted. Fish assemblages above such gates were generally dominated by primarily freshwater species, as compared with primarily saltwater (estuarine-marine) species below. The conversion of the great majority of small mangrove-fringed tributaries in the lower reaches of this river system into uniform floodgated drainage channels has thus resulted in the destruction of, and impeded fish access to, large areas of previously available estuarine fish nursery and feeding habitat. These drainage changels are now dominated by terrestrial-freshwater vegetation above where they are cut off from the main river channels by the floodgates, and the period of their construction has coincided with that of reported declines in fish catches in this river system. On the basis of the above findings, it is recommended that these floodgates be left fully open at all times except immediately prior to and during floods in the river system, thus facilitating the re-establishment of fringing mangrove vegetation along the banks of the artificial drains in the lower reaches, generally improving flushing and thus water quality in these drains, and allowing the establishment of primarily estuarine-marine fish communities, including more species of economic importance, in them.     

金沙江下游梯级水库运行期设计洪水及汛控水位

研究探讨梯级水库运行期设计洪水计算理论和方法,实现防洪和发电效益最大化。采用t-Copula函数建立各分区洪水的联合分布,通过蒙特卡罗法和遗传算法(GA)推求金沙江下游梯级水库的最可能地区组成;分析计算各水库运行期的设计洪水及汛控水位。结果表明:①最可能地区组成结果合理可靠,可为梯级水库运行期设计洪水的分析计算提供依据;②金沙江下游梯级水库受上游水库调蓄影响显著,向家坝水库1000年一遇设计洪峰15400m^3/s(35%),3d、7d和30d洪量的削减量(削减率)分别为35.6亿m^3(33%)、70.2亿m^3(30%)和85.0亿m^3(11%);③在不降低防洪标准的前提下,下游各水库在运行期汛控水位相比汛限水位可适当抬高,白鹤滩、溪洛渡和向家坝水库的汛控水位(汛限水位)分别为788.82m(785m)、570.67m(560m)和371.36m(370m),汛期年均发电量分别增加2.1%、6.1%和1.4%,年增发电量17.1亿kW·h。     

分期设计洪水频率与防洪标准关系研究

现行分期设计洪水模式估算的分期设计洪水值均小于或等于年最大设计值,达不到规定的防洪标准。采用Gumbel-Hougaard Copula函数描述两个分期的分期最大洪水之间的相关性结构,并构造边缘分布为P-Ⅲ分布的分期最大洪水联合分布,建立分期最大洪水与年最大洪水的关系式,讨论分期设计洪水频率与防洪标准应满足的关系,探讨能够满足防洪标准的新的分期设计洪水模式。应用示例表明,新模式主汛期设计值相对年最大设计值小幅度增加,而非主汛期设计值则小于年最大设计值,既满足不降低防洪标准的要求又能够起到优化设计洪水的作用,为分期设计洪水研究提供了一条新的思路。     

长江中下游河湖洪水演进的数值模拟

以长江中下游(宜昌-大通)防洪系统为对象,在水文、河道及湖盆地形现状条件下,建立了一个能适应各种复杂条件的一二维非恒定流模型,来进行长江干流、河网、湖泊、分蓄洪区垸及水库的洪水演进和调度仿真.所建模型的洞庭湖部分采用无结构网格二维非恒定有限体积格式,以适应湖区复杂的边界形状和保持水量平衡.河网区部分采用一维非恒定流显隐结合的分块三级算法,以准确实现河网汊点流量的自动分配和往复流动.为了提高模拟精度和扩展模拟功能,在水流数值模拟的范围内侧重讨论了内外动边界处理、分蓄洪运用及阻力项计算等环节,提出了合理可行的数值处理方法.采用20世纪80年代至90年代共6年汛期洪水资料对所建模型进行了严格的率定和检验,高精度的模拟结果证实了模型的合理性和有效性.     

卫河流域河流地下水流系统氮素运移的数值模拟

卫河是海河流域污染最严重的河流之一,该河如何影响附近浅层地下水的水质是长期受到重视但缺乏定量研究的关键问题。为探讨这一问题,利用Hydrus 2d模型模拟河流非饱和带氮素的迁移转化,以GMS软件中的RT3D模块模拟氮素在饱和含水层中的运移,将包气带底部淋滤出的污染物浓度定为饱和带溶质运移模型的上边界条件,首次实现了河流非饱和带饱和含水层氮素运移的联合模拟,得到河流线状污染源对浅层地下水的影响程度及范围。研究结果表明：由于吸附作用、硝化反硝化作用的存在,从河流上游到下游,包气带厚度加大,运移至含水层中的NH4-N、NO2-N浓度呈下降趋势,而NO3-N浓度则呈上升趋势。随着入渗时间的增长,进入饱和含水层中的NH4-N、NO2-N、NO3-N的浓度逐渐升高并最终保持稳定。污染的河流对浅层地下水的影响呈带状分布,污染物随入渗水流在包气带中垂直入渗;在饱和含水层中以水平运移为主,污染羽偏向地下水流动的方向,其影响距离不超过500 m。     

矿井顶板水害预测与防治专家系统

影响顶板水涌出的因素是多方面的，不仅与含水层本身的类型、特征、赋存条件有关，而且还与煤层顶板各隔水岩层的水文地质条件、地层结构及采矿地质条件有关。本文在分析矿井顶板水危害现状及相关专家系统研究概况的基础上，研究了顶板富水性分区的影响因素，以信息拟合方法完成了顶板富水性分区，并以此为基础，结合模糊理论，完成了综合模糊评判决策系统，最后进行了实例验证。