Estimating discharge in gravel‐bed river using non‐contact ground‐penetrating and surface‐velocity radars

Discharge measurement is a critical task for gravel‐bed channels. Under high‐flow conditions, the elevation of the riverbed changes significantly by intensive torrential flow. The stage–discharge relations commonly used for stream discharge estimation may no longer be adequate. The contact‐type velocity measuring is also subject to measurement errors and/or instrument failures by the high‐flow velocities, driftwood, stumps, and debris. This study developed a new real‐time method to estimate river discharge in gravel‐bed channels. A systematic measuring technology combining ground‐penetrating radar and surface‐velocity radar was employed. The rating curves representing the relations of water surface velocity to the channel cross‐sectional mean velocity and flow area were established. Stream discharge was then deduced from the resulting mean velocity and flow area. The proposed method was examined in a steep gravel‐bed reach of the Cho‐Shui River in central Taiwan. The estimated stream discharge during three flood events were compared to the prediction by using the stage–discharge relation and the index‐velocity method. The proposed method of this study is capable of computing reasonable values of discharge for an entire flood hydrograph, whereas the other two methods tend to produce large extrapolation errors. Moreover, when the computed discharge is used in 2D flood flow simulation, the proposed method demonstrates better performance than the commonly used stage–discharge and index‐velocity methods.     

Quantifying Whitewater Recreation Opportunities in Cataract Canyon of the Colorado River,Utah: Aggregating Acceptable Flows and Hydrologic Data to Identify Boatable Days

The structural norm approach was combined with the Potential for Conflict Index to define recreation streamflow needs for the Colorado River in Utah and Colorado. An online survey was completed by 128 commercial and non‐commercial boaters, who evaluated a range of flows for whitewater boating. For the Cataract Canyon reach, respondents rated the quality of their recreation experience of specific flows, describing the quality of boating opportunities across the full range of historical streamflows. Ranges for both acceptable and optimum flows were defined, as well as thresholds for unacceptable flows. These ranges were then evaluated against historical hydrologic records to quantify the timing, frequency, and duration of days when defined whitewater flows exist across different year types (i.e. average boatable days). Results indicated that on average, a total of 257 boatable days existed in dry years, and 353 total boatable days occurred in dry‐typical years. In wet and wet‐typical years, 362 and 365 total boatable days respectively, occurred on average. Results of the boatable days' analysis indicated that over the 23‐year period of record, whitewater boating opportunities occurred nearly every day of the year in all but the driest year types. Results from this study provide resource managers with information which can be used in the development of annual operating plans for the Colorado River Basin and help managers understand how changes in flow impact the quality of recreational opportunities. This application demonstrates the value of analysing boatable days on any river where recreation management is a priority. Copyright © 2016 John Wiley & Sons, Ltd.     

The Importance of Shallow‐Low Velocity Habitats to Juvenile Fish in the Middle Mississippi River

Habitat management is a crucial aspect of fisheries management. Without knowledge of habitat associations, fisheries scientists are unable to effectively make habitat conservation or restoration recommendations. This becomes especially prominent when trying to manage commercially harvested populations and protect threatened or endangered species. To determine juvenile fishes habitat associations in the Middle Mississippi River, we analysed mini‐trawl catch data of six common juvenile fish species: blue catfish (Ictalurus furcatus), channel catfish (Ictalurus punctatus), channel shiner (Notropis wickliffi), freshwater drum (Aplodinotus grunniens), paddlefish (Polyodon spathula), and shovelnose sturgeon (Scaphirhynchus platorynchus). Overall, we conducted 2251 mini‐trawl sampling efforts between 2002 and 2013, resulting in the capture of 23,742 target specimens. Catch per unit effort was evaluated by structural habitat (i.e. velocity, depth, and substrate). Overall, these data suggest that juvenile fish species are more prevalent in shallow water and slower velocities. Ultimately the information garnered during this evaluation should be incorporated when considering habitat modifications, especially those modifications that impact the availability of shallow‐low velocity habitats. Copyright © 2016 John Wiley & Sons, Ltd.     

Benchmarking Fluvial Dynamics for Process‐Based River Restoration: the Upper Rhine River (1816–2014)

Multi‐temporal analysis of river‐floodplain processes is a key tool for the identification of reference conditions or benchmarks and for the evaluation of deviations or deficits as a basis for process‐based river restoration in large modified rivers. This study developed a methodology for benchmarking fluvial processes at river segment level, focusing on those interrelations between morphodynamics (aggradation, erosion, channel shift) and vegetation succession (initial, colonization, transition) that condition habitat structure. Habitat maps of the free‐flowing Upper Rhine River downstream from Iffezheim dam (France–Germany border) were intersected with a geographic information system‐based approach. Patches showing trajectories of anthropization, changeless, progression and regression allowed for the identification of natural and human‐induced processes over almost 200 years. Before channelization, the riverine system was characterized by a shifting habitat mosaic with natural heterogeneity, high degree of surface water connectivity and equilibrium between progression and regression processes. On the other hand, the following 175 years of human interventions led to severe biogeomorphologic deficits evidenced by loss of natural processes and habitat heterogeneity, hydrological disconnection between the river and its floodplain and imbalance of progression versus regression dynamics. The main driving forces of change are found in hydromorphological impacts (channelization, regulation and hydropower plant construction). Regression processes are now almost absent and have to be the objective of process‐based river restoration measures for the studied river‐floodplain system. A sustainable view on water management and river restoration should aim at a more resilient riverine system by balancing the recovery of natural processes with societal needs. Copyright © 2016 John Wiley & Sons, Ltd.     

制备工艺对C3D/EP复合材料力学性能的影响

本文采用了两种工艺制备三维编织碳纤维增强环氧树脂基(C3D/EP)复合材料,并对其力学性能和微观结构进行了研究和分析.结果表明,孔隙对复合材料的影响较大,相对RTM工艺制备的复合材料,真空浸渍法制备的复合材料有较高的空隙率,较低的弯曲强度和弯曲模量、较好的冲击性能.     

热压辅助先驱体裂解制备Cf/SiC复合材料的研究

以聚碳硅烷为先驱体 ,采用先驱体转化法制备三维编织Cf SiC复合材料。研究发现 ,第一次裂解时采用热压辅助可以明显提高材料的致密度和力学性能。第一次在 160 0℃、10MP的条件下热压裂解 60min ,后续真空浸渍—常压裂解处理五个周期所制得的材料具有较高的力学性能 ,其弯曲强度和断裂韧性分别为 5 64MPa、16MPa·m1 2 。讨论了制备工艺对材料结构和性能的影响     

人工湿地净化富营养化河水试验研究(二)——基质层及流态对氮素污染物净化效果的影响

通过中试试验研究了基质层及流态对人工湿地净化富营养化河水中氮素污染物的影响情况,结果表明：砾石基质层厚度从80cm增加到120cm对湿地池净化氮素污染物的效果没有明显影响;将上层砾石替换为沸石后,湿地池对NH3-N的净化效果明显提高,说明不同的基质材料对NH4＋具有良好的选择性吸附作用,而将上层砾石替换为炉渣后湿地池对氮素污染物的净化效果几乎没有变化;在4种湿地流态中,复合流态（垂直流＋潜流）湿地池对TN、NH3-N、NO3-N的去除率均为最高,且与潜流-垂直流相前后次序没有显著相关性;潜流、垂直流湿地池对氮素污染物的去除率介于复合流、表面流之间;表面流最低.     

新形势下做好长江入河排污口管理的思考

从长江流域水质现状、入河污染物排放基本情况及国家关于长江经济带绿色发展的总体要求出发,分析了长江水资源保护面临的形势;从长江入河排污口区划、审批、监管及基础工作方面,对入河排污口管理现状进行了简要总结,并对存在的问题进行了梳理。基于长江入河排污口管理面临的形势,提出了长江委强化长江入河排污口管理的总体思路和重点工作,可以为新形势下做好长江入河排污口管理提供参考。     

对口丁坝双岸整治对黄河下游河道冲淤的影响

选取低含沙水沙系列、枯水多沙水沙系列以及规划设计的未来50 a水沙系列,利用黄河下游一维水沙数学模型,模拟计算了对口丁坝双岸治理方案下黄河下游河道在3种水沙系列条件下的冲淤状况。结果表明,游荡性河段采用对口丁坝方案整治后,输沙能力得到了提高,该河段多输送的泥沙一半以上输送到利津以下,其余部分淤积在高村—利津河段,其中淤积以高村—艾山河段为主,艾山—利津河段的冲淤情况与现状相比变化不大。