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Hydrologically Based Environmental Flow Methods Applied to Rivers in the Maritime Provinces (Canada)
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The demand for water withdrawal continues to increase worldwide. These water withdrawals from rivers can affect fish habitat and aquatic life. As such, environmental flow assessment methods are used in order to protect rivers against excessive water withdrawals. The concept of environmental flow relates to the quantity of water required in rivers to sustain an acceptable level of living conditions for aquatic biota at various phases of their development. For many agencies, environmental flow methods are essential in environmental impact assessments and in the protection of important fisheries resources. The present study deals with the evaluation of hydrologically based environmental flow methods within the Maritime Province of Canada. In total, six hydrologically based environmental flow methods were compared using data from 52 hydrometric stations across the region. Some methods provided adequate environmental flow protection (e.g. 25% mean annual flow and Q50 flow duration method); however, other methods did not provide adequate flow protection (e.g. Q90 flow duration method and 7Q10 and 7Q2 low‐flow frequency). The 70% Q50 method provided adequate flow protection only under good baseflow conditions and should be applied with extreme caution. The present study shows the importance of the hydrologic flow regime, particularly as it pertains to the baseflow component, as a significant determinant in the level of instream flow protection. © 2014 Her Majesty the Queen in Right of Canada. River Research and Applications © 2014 John Wiley & Sons, Ltd. 相似文献
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AN APPROACH IN MODELING TWO-DIMENSIONAL PARTIALLY CAVITATING FLOW 总被引:10,自引:7,他引:3
1. INTRODUCTIONCavitation is a phenomenon that widely occurs in liquids. When the flow leads to the local pressure below the saturation vapor pressure of water (the fluid medium, in our research), usually incipient cavitation firstly occurs on the solid b… 相似文献
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The natural flow paradigm (NFP) emphasizes the need to partially or fully maintain or restore the range of natural intra‐ and interannual variation of hydrologic regimes to protect native biodiversity and the evolutionary potential of aquatic, riparian and wetland ecosystems. Based on our studies of natural and managed flow regimes in New Zealand, we do not believe that all components of the natural flow regime are necessary to achieve the objectives of the NFP, either partially or fully, because many aquatic species have very flexible niches and life‐history requirements (i.e. there is ‘ecological redundancy’). Obviously, maintaining the natural flow regime will maintain the hydrologic and hydraulic conditions necessary for sustaining natural ecosystems. However, if there is adequate knowledge of what ‘values’ need to be maintained in a waterway, and the aspects of the flow regime that are required to maintain those values are also known, then regimes can be designed that target these requirements and thus optimize conditions for the ‘values’. We believe that an assessment of ecosystem requirements using information on river processes together with habitat requirements and life‐history strategies of biota can achieve the best balance between resource use and sustaining ecosystem function and value, and show examples where changes to natural flow regimes have maintained, or even improved, instream values in some New Zealand rivers. We caution that simple flow‐based rules, such as those that might be developed under the NFP, could be unnecessarily restrictive on multiple use of water in New Zealand while, at the same time, preclude the opportunity for enhancement of key ecosystem values in many waterways. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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本文介绍了混合流的概念,结合某一中型水库的试验,观测了混合流在抬高尾水时的下游流态。流速分布的变化规律以及对消能效果的影响。从而说明了低水头泄洪建筑物利用挑流消能有更多的可能性。 相似文献
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Liu Fa-quan 《水动力学研究与进展(B辑)》1999,(1)
1.INTRODUCTIONInthedesignofanovertoppedrock--filldam,oneofthemajortasksistodecidethesizeofthedownstreamprotection.Theovertoppedrock--filldamismadeofporousmedia,thereforethewaterwillpenetrateintothedamfromtheupperfaceandemergeoutofitfromthelowerpart,whileitflowsoverthedam.Hence,theprotectionissubjectedtotheactionofboththeoverflowandtheseepageflow,andneitherofthemcanbenegligible.Inthiscase,theflowfieldconsistsoftwoparts:theopenflowandtheseepageflow,whichhavedifferentproperties.Infact,forthe… 相似文献
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本文利用计算机可视化的方法对直槽流动的数值模拟结果进行了处理,得到了若干组显示涡量场和涡管运动变化的计算机动画,通过对这些直观的动画进行分析,发现了直槽流动失稳的一些现象,对于流动稳定性的研究具有一定的参考价值。 相似文献
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低含沙水流运动特性综述 总被引:6,自引:2,他引:4
本文着重综述了清水水流、挟沙水流的流速分布动特性、能量间分配关系等流动现象的内部规律,并系统分析比较了它们的异同,文中还兼论了卡门常数。 相似文献
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内、外边界定压条件下地层压力的解 总被引:1,自引:1,他引:0
本文在内、外边界定压的条件下得到了平面单向流和平面径向流两种渗流形式在拉氏空间的解析解,利用Stehfest数值反演方法给出了地层各点的压力分布曲线,由这些曲线可以清楚地看到流体的流动由不稳态流向稳态流过渡以及最后达到稳态流的过程。本文给出的压力解可用于准确预测油井(或水井)由开井达到稳定生产所需要的最小时间,同时也是对油藏渗流力学基础理论的一个有意义的补充。 相似文献
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主要从坡面流流态对坡面流阻力的影响、坡面流阻力与雷诺数的关系、降雨对坡面流阻力的影响、坡面流阻力公式4个方面对前人关于坡面流阻力的研究成果进行了总结。结果表明:坡面流流态的不确定性导致了坡面流阻力变化更为复杂;坡面流阻力与雷诺数之间并无良好单一的相关关系;降雨对坡面流阻力有很大的影响作用但具体影响机理并未有明确的结论;坡面流阻力公式表征仍用明渠水流概念及表达方式,并且3个阻力系数n、f、C哪个更适合表征坡面流阻力尚无统一的结论。进而对目前存在的问题进行了分析,对今后的发展进行了展望,认为需在研究方法和实验设备及量测技术方面有所突破,才可以更好的对坡面流阻力进行全面系统的研究。 相似文献
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管流与明渠流同属流体力学中的内流,其总流机械能方程在水力学中称为总流能量方程。现有水力学中的总流能量方程是以理想不可压缩液体的伯努利方程为基础得到的,无法得到总流机械能损失的表达式。该文作者曾直接从黏性不可压缩流体运动的控制方程出发分别得到了管流及明渠流的总流机械能方程,解决了以上问题。考虑到层流条件下明渠流自由表面的变形特点,该文在前述工作基础上,将管流及明渠流在层流条件下的总流机械能方程进行了统一,同时还分别计算了管流(圆管、不同长短半轴比的椭圆管、不同宽高比的矩形管和不同内外径比圆环管)及明渠流(不同宽深比的矩形明渠)在层流条件下的总流机械能损失系数。结果表明:在同一雷诺数条件下,圆管层流的总流机械能损失系数比椭圆管层流、矩形管层流、圆环管层流及较大宽深比的矩形明渠层流的机械能损失系数要小。 相似文献
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NUMERICALSTUDYONTHEVORTEXSTRUCTURESINTHEWAKEOFANOSCILLATINGCIRCULARCYLINDERINAUNIFORMFLOWLuXi-yun;TongBing-gang;ZhuangLi-xian... 相似文献
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Sun Li-tan 《水动力学研究与进展(B辑)》1996,(3)
APPLICATION OF MILES-HOWARD THEOREM TO STUDY THE INSTABILITY OF ATMOSPHERIC GRAVITY WAVES ON A HETEROGENEOUS ORTHOGONAL SHEAR... 相似文献
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黄梅 《广东水利电力职业技术学院学报》2009,7(3)
为提高他什店站径流量统计成果精度,减小由于流量测次分布不够,而使得流量资料整编时所推算出的径流量存在一定的误差。通过对比分析,选择一种既降低单次测流的工作量并缩短测流时间、同时所测流量的测验误差符合规范规定的流速仪流量测验方法,用这种方法增加每日流量测验的次数,尽可能达到能反映流量日变化的过程,提高用连实测流量过程线法进行流量资料整编的精度,进一步提高径流量统计成果的精度。 相似文献
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INVESTIGATION ON THE SPLASH LENGTH OF THE AERATED JET 总被引:5,自引:2,他引:3
Liu Shi-he Qu BoSchool of Water Resource hydropower Wuhan University Wuhan China e-mail: shihe @ .com 《水动力学研究与进展(B辑)》2003,15(6)
Atomized flow forms as an aerated jet from high dams impacts against the downstream water surface at high speed. Of all the regions of atomized flow the splash region is in the center of storm rainfall, which might cause certain damage to the hydropower stations and thence more attention should be paid. In this paper the impact of the water drop at the outer edge of the aerated jet against the downstream water surface was analyzed, and the motion of the splash water drop was investigated. Furthermore, a new formula for the calculation of the splash length was suggested, which is in good agreement with the data of model tests and prototype observation. 相似文献
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An experiment concerning the sound propaga-tion in aerated open channel flow was designed and conductedin a variable slope chute. The acquisition of sound data wasdone by the hydro-phones installed into the bottom wall of thechute. The data were analyzed and processed by the tape re-corder and a 3562A analyzer. The primary experimetal resultsindicated that the sound speed in aerated flow is varied with the air concentration and highly lower than each of the soundspeed in pure water or air. As released by the derived theoryformula, the minimum sound of 24m/s in aerated flow hap-pened when the air concentration achieved to 50%. This resultshows that the compressibility of high speed aerated flowshould be considered when the air concentration is near to50%. A criterion of compressibility of high speed aerated flowwas also giv. En in this paper. 相似文献