Plant functional types in Lake Nubia in relation to physicogeographic factors

The shoreline vegetation of Lake Nubia in Sudan was studied by means of morphological characteristics and functional traits of plants established-phase as published in literature reviews. The 57 species recorded in 83 sampling sites were classified according to 15 morphological traits into six Plant Functional Types (PFTs), using Two Way Indicator Species Analysis (TWINSPAN). Principal component analysis (PCA) was used to evaluate the homogeneity of these groups in terms of their traits. The resulting PFTs were related to the physicogeographical variables measured (soil texture, soil moisture, soil thickness and elevation) using canonical correspondence analysis (CCA). The ratios in occurrences of the functional types were calculated per each moisture segment, and can be used as an indicator of the shoreline dynamics.     

TOWARDS A BETTER FORECAST FOR RESERVOIR SLOPE SLIDING

The siltation of reservoir causes many problems of management and environmental disturbances that are important to minimize. Solving these problems requires in particular a good knowledge of mud bank instabilities. In partnership with the Laboratoire National d'Hydraulique (LNH), a subsidiary of Electricite de France (E.D.F.), authors realize a study of soft soils sliding entailed by reservoir emptying. Using a geotechnical flat sliding mechanism, the theoretical formulation of the safety factor can be established when the sediment mass is submerged and emergent. The measurement campaign carried out makes it possible to obtain bathymetric and topographic surveys and a geotechnical characterization of the soil for the whole reservoir of Grangent dam, located on the Loire (France). The proposed model appears to agree satisfactorily with the instability of the zones emerged because of the emptying and with the stability of the profile after emptying. The use of this model within the framework of forecasts     

The engineering geology of the Tabarak Abad Dam

The Tabarak Abad Dam on the river Tabarak, a branch of Atrak river, is located about 25 km of northeast of Quchan city in the northeast of Iran. The dam is now under construction and will be completed in 2002. The Tabarak Abad Dam has been designed as an earthfill dam with a clay core. The dam and its associated concrete structures are mainly founded on limestone and shale of the Shoorigeh formation of Upper Jurassic to Lower Cretaceous age and limestone and sandstone of the Tirgan formation of Lower Cretaceous age. These rocks are affected by high jointing and faulting especially in the surface. This paper discusses the site investigation for the dam.     

水布垭水电站坝基岩体地质模型研究

围绕水布垭水电站坝基地质模型研究 ,开展了工程地质调查、岩石力学室内外测试和试验和工程应用的研究。在大量野外工作及理论分析的基础上 ,详细研究了水布垭水电站工程地质岩组 ,地质构造规律及坝基岩体地应力和水文地质条件 ,建立了坝基岩体的概化地质结构模型。开展了针对坝基基本地质模型单元的岩体质量评价 ,提出了坝基基本地质模型单元的岩体力学参数     

流域水环境监测管理系统设计与应用——以云南松华坝流域为例

流域水环境监测管理系统建设将对当地水环境信息化建设和业务部门工作效率提高起到促进作用,为水环境管理与保护决策提供必要依据。文章对信息采集、传输、主要技术和系统总体结构做了研究.介绍了系统功能和实现方法。系统本着低成本、开发简单、快捷、方便的原则,采用可视化开发工具、GIS组件、Access数据库集成模式,开发C/S结构的应用系统。系统实现了基本GIS功能、信息管理、水质模拟、水环境容量计算、污染源分析等功能,满足当前业务数据分析管理需要,达到了一定辅助决策的目的。     

三峡坝区水体吸收系数的特征研究

利用2007年11月在三峡坝区现场实测的水色要素吸收系数数据,对总颗粒物、浮游植物、CDOM的吸收系数特征进行了分析和研究。结果表明,对于三峡坝区区域的水体:(1)总颗粒物吸收光谱分布与非藻类的吸收光谱相似;(2)非藻类颗粒物的吸收系数随波长的变化分布接近指数衰减规律,且不同波段的吸收系数之间存在一定的关系;(3)多项式关系能较好的表达浮游植物吸收系数与叶绿素a浓度之间的关系;(4)分段函数能很好的表达CDOM的吸收系数特性,对500nm以下光谱的吸收呈现负指数衰减的规律,不同采样点拟合精度R2接近1;501—700nm波段范围的光谱曲线采用多项式能进行很好的拟和,且拟合精度R2达到95%以上。     

都江堰震后土地利用/覆被变化信息提取方法研究

快速和精确评估"5·12"汶川地震后的土地利用/覆被变化对科学减灾、灾后重建及生态环境恢复具有重要意义。常规方法从遥感图像上提取土地利用/覆被变化信息时,多以研究区整体为处理对象,直接对全图像进行分类提取,容易忽略地形地貌和地质构造等背景因素对分类结果的影响。本文以都江堰为试验区,根据地质构造展布特征及地形地貌发育形态将其分成平原区(Ⅰ区)、低山区(Ⅱ区)、中高山区(Ⅲ区)和高山区(Ⅳ区)。对Ⅰ区采用ISODATA方法进行非监督分类;对Ⅱ区和Ⅲ区分别采用最大似然(ML)分类法进行监督分类;对Ⅳ区采用人机交互解译方法进行分类。试验结果表明,基于地理地质环境的分块分类方法是高效、精确的。     

随机森林回归模型的悬浮泥沙浓度遥感估算

三峡工程蓄水以来,清水下泄,坝下游河段发生了长时间、长距离的沿程冲刷,河流悬浮泥沙浓度发生改变,给沿岸生态系统带来了不利影响。随机森林算法灵活、稳健,已被广泛应用于各类生态环境变量的回归预测分析,但其在水体悬浮泥沙浓度估算方面的能力尚未得到充分认识。基于泥沙站点监测数据和MODIS卫星遥感反射率数据,通过构建随机森林非参数回归预测模型,对三峡工程坝下游宜昌至城陵矶河段在建坝前后14年间(2002年—2015年)各月的悬浮泥沙浓度进行遥感估算。研究表明:(1)基于随机森林的悬浮泥沙浓度估算模型表现较好,模型预测值与实测值间相关性好、预测精度高,优于其他模型(线性回归、支持向量机、人工神经网络模型)。(2)在参与模型构建的MODIS波段变量中,红波段被认为是最重要的预测变量,但不能单独使用它进行预测,悬浮泥沙遥感预测需要多变量共同参与。(3)将悬浮泥沙数据按季节分类所构建的随机森林模型,其平均误差为0.46 mg/L,平均相对均方根误差为12.33%,估算效果最优,能够满足较高精度下悬浮泥沙浓度估算的需求。综上,可以考虑以季节为划分依据,用随机森林回归模型估算悬浮泥沙浓度,并用于后期坝下游河道悬浮泥沙浓度时空反演。     

淮南六方堤多层土堤基塑流稳定性计算

本文研究了台阶状六方堤堤体荷重的弗里哀级数展开式和堤基应力计算系数的计算原理,通过堤基应力计算和塑流判别,对六方堤多层土堤基塑流稳定性进行了评价。     

Optimizing the dataset size of a topo-bathymetric survey for Hammam Debagh Dam,Algeria

The capacity of water reservoirs may be considerably reduced by sediment transport and accumulation. This phenomenon may occur quickly in regions prone to erosion, such as Hammam Debagh Dam region in Algeria. For better management of water resources, it is important to estimate the volume of a reservoir by regular and frequent topo-bathymetric surveys. Topo-bathymetric surveys with a high point measurement density are expensive and time-consuming. To reduce this expense and to increase the frequency of topo-bathymetric surveys, it is required to optimize their size and density. The complete survey of the reservoir created by the Hammam Debagh Dam in Algeria was examined in comparison with 19 reduction subsets using geostatistics. The study showed that the complete dataset of 32,164 points, corresponding to a density of 42 points ha^-1 could be reduced to 10,000 points, i.e. 13 points ha^-1, without affecting the estimation of the water volume in the reservoir. This reduction could considerably simplify the work load, reduce the expenses to do these surveys, and, therefore, allow for an increased frequency of topo-bathymetric surveys.