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1.
Freshwater fishes are threatened globally, and often too little is known about threatened species to effectively guide their conservation. Habitat complexity is linked to fish species diversity and persistence, and degraded streams often lack habitat complexity. Beaver Castor spp., in turn, have been used to restore streams and increase habitat complexity. The northern leatherside chub Lepidomeda copei is a rare, small‐bodied, drift‐feeding minnow that has anecdotally been observed to use complex habitats associated with beaver dams in the western United States. To investigate this anecdote, we conducted fish and habitat surveys, the latter focusing on quantifying habitat complexity, in a sub‐basin of the Upper Snake River Basin in the USA. Complementary generalised linear model and path analyses revealed that northern leatherside chub occurred more often at sites with complex streamflows, and streamflows were more complex when beaver dams were present and pools were deeper. Northern leatherside chubs were also more likely to occur when temperatures were warmer, aquatic macrophytes were abundant and stream channels were narrow and deep. The linkage between chubs, complex streamflows and beaver dams needs to be evaluated more broadly to completely understand its role in the rangewide status of the species. However, it does suggests that increased use of beaver reintroductions and dam analogues for stream restoration could be a boon for the northern leatherside chub, but such efforts should be monitored to determine their effectiveness to help adapt beaver‐based restoration approaches to best benefit the species. 相似文献
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全球气候暖干化对秦岭南北河流径流泥沙的影响研究 总被引:8,自引:12,他引:8
以秦岭南侧汉江和北侧渭河多年的径流泥沙观测资料,分析了全球气候暖干化对秦岭南北径流泥沙的变化。分析指出在80年代后,由于全球气候变化的影响,秦岭南北河流年均径流量均减少,与1935-1980年相比,汉江河流年均径流量减少1.9%,渭河河流年均径流量减少27.4%;同时汉江河流泥沙含量明显减少,但渭河河流泥沙含量呈增加趋势,是汉江河流泥沙含量133倍,表明了秦岭南北两侧在全球气候暖干化表现出明显的区域响应性。 相似文献
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对砌石拱坝的加高倍厚中新、老坝体结构面,用有限元软件ANSYS结合接触理论进行计算,并分析结果得出:温升、水压力和淤沙压力使结合面上的接触压力增大,从而接触摩擦应力较大,有利于结合面的结合,而结合面在温降的作用下有脱离的趋势。 相似文献
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The influence of the structure and location of dam and weir on fluid flow state in a two-strand tundish is studied, and a set of optimal structure, combining with the average residence time calculated from RTD curve, is obtained. The result indicates that the fluid flow state can be changed and the path of the fluid flow can be prolonged as well as the average residence time is improved after using dam and weir. But there are some dead zones after fluid passed through the dam and weir. Combination scheme of No. one dam and weir is better than the others. Its average residence time is 299 s and the volume fraction of dead zone is 31.0%. After the optimization of flowing control parameters in tundish, the best case is that the distance between dam and weir is 290 mm and the distance between weir and the long nozzle is 383 mm. The longest average residence time is 351 s and the minimum volume fraction of dead zone is 19.0% under the above situation. Compared with that of no dam and weir, the average residence time increases by 65 s and the dead zone volume fraction decreases by 15.0%. Based on Newton formula, the calculated results show that the inclusions with diameter larger than 17.5 μm can float up within 351 s under this optimization situation. 相似文献
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以淤泥类软土的动力特性为基础发展起来的振动挤淤法,在标准海堤软土地基处理中有其独特的实用性。根据海堤的工程特点,分析了振动挤淤法在处理海堤软土地基的必要性和可行性。并着重阐述了振动挤淤法中3个关键施工参数的理论分析和工程实践,这3个参数包括:基础埋深,最小垫层厚度,施工机械作业参数。 相似文献
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林诚魁 《中国农村水利水电》1995,(10)
碾压混凝土具有施工速度快,水泥用量少,投资省等明显的优点。国内的理论研究和工程实践都取得了突飞猛进的进展,在防渗问题方面也进行了卓有成效的探索,如福建省几座已建成的碾压混凝土坝均采用不同的防渗类型。文章结合福建省重点工程连江山仔水利枢纽工程碾压混凝土坝的施工情况,介绍了能够充分发挥碾压混凝土坝快速施工特点的悬臂钢模、改性混凝土的施工方法,论述了喷丙乳砂浆作为碾压混凝土坝上游主防渗体与这一施工特点相统一所具有的优越性。 相似文献
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为了实现大坝整体结构、安全监测测点布置及监测成果的可视化展示功能,并且能够及时、准确地掌握大坝运行状态和异常情况,以甘再碾压混凝土重力坝为例,对传统大坝安全监测系统存在的问题进行了深入的分析与解答,并围绕问题提出了可视化的大坝安全监测系统思想,利用Revit、Dynamo、Civil3D等主流BIM软件建立了大坝主体结构及监测点的模型族库,集成了大坝及监测系统的三维可视化BIM模型.借用于BIMFACE平台轻量化技术、PHP脚本语言和MySQL数据库等现代化信息技术,开发出基于B/S架构的甘再大坝安全可视化系统,实现了BIM模型的Web轻量化展示,可通过客户端浏览器在三维模型中直观查看大坝结构、监测仪器信息以及监测点时程曲线变化等内容.通过本系统的应用,大大提高了大坝运行期间安全监测的可视化管理水平,同时对传统的大坝安全监测系统提出了现代化的建立方式与思想. 相似文献