Influence of a high‐head dam as a dispersal barrier to fish community structure of the Upper Mississippi River

In river systems, high‐head dams may increase the distance‐decay of fish community similarity by creating nearly impermeable dispersal barriers to certain species from upstream reaches. Substantial evidence suggests that migratory species are impacted by dams, and most previous studies in stream/river networks have focused on small streams and headwaters. Here, we assess whether a high‐head dam (Lock and Dam 19; LD 19) on a large river, the Upper Mississippi River (UMR), substantially alters fish community structure relative to variability expected to occur independent of the dam's effect as a fish dispersal barrier. Using fish catch per unit effort data, we modelled the distance‐decay function for the UMR fish community and then estimated the similarity that would be expected to occur across LD19 and compared it with measured similarity. Measured similarity in the fish community above and below LD19 was close to the expected value based on the distance‐decay function, suggesting LD19 does not create an abrupt transition in the fish community. Although some migratory fish species no longer occur above LD19 (e.g., skipjack herring, Alosa chrysochloris), these species do not occur in high abundance below the dam and so do not drive variation in fish community structure. Instead, much of the variation in species structure is driven by the loss/gain of species across the latitudinal gradient. Lock and Dam 19 does not appear to be a clear transition point in the river's fish community, although it may function as a meaningful barrier for particular species (e.g., invasive species) and warrant future attention from a management perspective.     

Sediment flux from Lesser Zab River in Dokan Reservoir: Implications for the sustainability of long‐term water resources in Iraq

Prudent management of Iraqi water resources under climate change conditions requires plans to be based on actual figures of the storage capacity of existing reservoirs. With the absence of sediment flushing measures, the actual storage capacity of Dokan Reservoir (operated since 1959) has been affected by the amount of sediment delivered during its operational life leading to an undetermined reduction in its storage capacity. In consequence, there has not been an update on the dam's operational storage capacity curves. In this research, new operational curves were established for the reservoir based on a recent bathymetric survey undertaken in 2014. The reduction in reservoir capacity during the period between 1959 and 2014 was calculated by the mean of the difference between the designed storage capacity and the storage capacity which was concluded from the 2014 bathymetric survey. Moreover, the rate of sediment transported to the reservoir was calculated based on the overall quantities of accumulated sediment and the water discharge of the Lesser Zab River into the reservoir. The results indicate that the dam capacity is reduced by 25% due to sedimentation of an estimated volume of 367 million cubic metres at water level 480 m.a.s.l. The annual sedimentation rate was about 6.6 million cubic metres, and the sediment yield was estimated to be 701.2 t?km^?3?year.     

三峡枢纽排漂孔及泄洪孔过流面检修装备方案研究

针对三峡工程排漂孔及泄洪孔过流面墙壁的检修分别提出了多种专用检修装备方案。经过分析比较,得出安全合理的检修装备方案。排漂孔检修方案:闸室段侧墙用升降台车,斜坡段侧墙采用单梁吊篮,排漂孔底板采用双侧单台车;泄洪深孔检修方案:闸室段和斜坡段侧墙采用升降台车检修,底面与排漂孔检修方案相同。     

“网河”非稳定流模型在洪泛区洪流演进中的应用

将宽阔的溃口洪水行进范围概化成由河道水塘和联系河道组成的网河,用一维非恒定流方程组来描述主要的水充运动状态,通过简化和变换,改写成统一的四点线性隐式有限差的方程组形式,再用双消除法求解,全部计算在微机上实现,参数用实测资料率定,成果具有较好的精度,在一定程度上反映出横水流方向的水位流量变化,为防洪水利计算开辟一条新的途径。     

液压卧倒闸坝在拦河坝工程中的应用

简述液压卧倒闸坝在江西省宜春市袁州区温汤镇防洪工程拦河坝中的应用。设计通过对多方案技术经济比选,推荐采用液压卧倒闸坝。可供类似工程参考。     

USING OTOLITH CHEMISTRY TAGS AND GROWTH PATTERNS TO DISTINGUISH MOVEMENTS AND PROVENANCE OF NATIVE FISH IN THE GRAND CANYON

Fish otolith and water chemistry were assessed in the Grand Canyon reach of the Colorado River and its tributaries. Aqueous strontium and selenium (in ratio to calcium) and carbon stable isotopic ratios were identified as markers with excellent potential to track the provenance and movements of the endangered humpback chub Gila cypha. Although otolith δ¹³C and Sr/Ca varied proportionately to water chemistry and provided a framework for detailed study of humpback chub movements, otolith Se/Ca showed ambiguous tracking of known water chemistries. As an application, we document the natal source and movement dynamics of n = 10 humpback chub and compare these findings from otolith microchemistry with the current paradigm of humpback chub spawning ecology. We found that seven of ten fish follow the current early life history paradigm and were spawned in the Little Colorado River and subsequently emigrated to the main stem Colorado River as juveniles. However, the otolith markers of three fish suggest an alternative early life trajectory with unknown provenance. Age and growth analyses demonstrate seasonally higher growth rates in the warmer Little Colorado River compared with the Colorado River. Combining natural markers with age and growth reconstructions provides a powerful tool for assessing the habitat use and success of humpback chub in the Grand Canyon. Copyright © 2012 John Wiley & Sons, Ltd.     

观音岩水电站右岸大坝首次基础固结灌浆生产性试验成果分析及建议

观音岩水电站右岸混凝土坝段坝基地质条件复杂,通过固结灌浆生产性试验,确定合理的施工参数和施工工艺措施,验证设计指标的合理性。本文对此加以介绍。     

基于加卸载响应比理论的大坝台风作用效应计算方法

台风对大坝的作用包括台风引起的强降雨对大坝的影响、台风引起的库水位波动(波浪)对大坝的影响以及台风风荷载对大坝的影响等。基于加卸载响应比理论,通过对台风作用下的大坝效应增强和维持判据进行深入研究,提出了库水位加卸载响应比和波浪加卸载响应比的计算方法,给出了台风作用下大坝效应增强与维持判据的评判准则。利用上述方法和评价准则,对受2010年10号台风"莫兰蒂"影响的东坞水库进行分析,结果表明,东坞水库大坝受台风影响不大,大坝处于稳定状态。将加卸载响应比理论引入到水利工程领域,是对加卸载响应比理论的应用范围的拓展,也是研究台风作用下大坝稳定性的新思路。     

Predicting dam failure risk for sustainable flood retention basins: A generic case study for the wider Greater Manchester area

This study aims to provide a rapid screening tool for assessment of sustainable flood retention basins (SFRBs) to predict corresponding dam failure risks. A rapid expert-based assessment method for dam failure of SFRB supported by an artificial neural network (ANN) model has been presented. Flood storage was assessed for 110 SFRB and the corresponding Dam Failure Risk was evaluated for all dams across the wider Greater Manchester study area. The results show that Dam Failure Risk can be estimated by using the variables Dam Height, Dam Length, Maximum Flood Water Volume, Flood Water Surface Area, Mean Annual Rainfall (based on Met Office data), Altitude, Catchment Size, Urban Catchment Proportion, Forest Catchment Proportion and Managed Maximum Flood Water Volume. A cross-validation R² value of 0.70 for the ANN model signifies that the tool is likely to predict variables well for new data sets. Traditionally, dams are considered safe because they have been built according to high technical standards. However, many dams that were constructed decades ago do not meet the current state-of-the-art dam design guidelines. Spatial distribution maps show that dam failure risks of SFRB located near cities are higher than those situated in rural locations. The proposed tool could be used as an early warning system in times of heavy rainfall.     

丰乐拱坝加厚新老混凝土结合处理效果评价

目前拱坝贴厚加固处理大多采用经验方法,为解决拱坝贴厚加固工程的安全性和经济性问题,采用ANSYS有限元计算程序对丰乐拱坝加厚新老混凝土结合处理措施进行非线性有限元分析。选取新老混凝土结合处理的锚杆设置参数(锚杆直径、间距、锚杆埋入老混凝土的深度)及参数水平作为变量,以正交试验设计的思想来安排有限元试验方案,并选取新老混凝土结合面的开裂度作为评价指标。计算结果表明,加厚处理时新老混凝土用锚杆联结可以有效地减小结合面的开裂度,并给出了经济有效的锚杆设置方案。