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为解决双库连通水库调洪演算问题,合理确定水库特征库容和水库对应的特征水位。本文以安徽省天长市焦涧水库为例,建立了双库调洪演算模型,得到了不同频率下设计洪水的调洪演算结果。计算结果表明,该方法理论合理,结果可靠,可作为水库除险加固设计及防洪运行调度的依据。 相似文献
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水库调洪演算可分为求解常微分方程和求解积分方程2种方法,其中求解积分方程方法在工程上运用更为广泛。目前工程上广泛使用求解积分方程方法多采用梯形法计算出库水量,使出库流量的计算精度相对偏低,对成果精度有一定的影响,可以研究加以改进。利用调洪积分方程和调洪微分方程,构建3次Hermite多项式拟合出库流量过程,再通过Simpson积分法计算出库水量,可构建出新的水库调洪积分方程,新方程中出库水量的计算结果可达到3次代数精度。新的水库调洪积分方程及其派生的误差传播方程在原方程的基础上增加了3次Hermite多项式拟合的影响项,是传统水库调洪积分方程的一种改进。采用不同的调洪时段对工程实例进行调洪演算,结果表明新方程对计算精度有一定的改善作用,可供工程技术人员参考使用。 相似文献
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水库防洪预报调度的风险分析 总被引:18,自引:4,他引:14
本文从水文预报误差的不确定性分析出发,将短期洪水预报精度评定指标转化为入库洪水过程的随机特征值,并引入水库调洪演算随机数学模型,从而实现水文预报风险向预报调度风险的转化,为定量考察预报调度风险率、合理选择动态的汛限水位提供了科学的依据。通过这一方法论证了水文预报精度对水库防洪预报调度风险率的影响,表明提高水文预报精度将有利于降低水库调洪风险率。 相似文献
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一、水库调洪演算概述水库调洪演算,是解决洪水期水库的水位与出流预报的关键。无论采用哪种方法进行调洪演算,其方法的基本依据都是联解以下两个方程: 相似文献
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《给水排水》2014,(9)
正As the eldest and most distributed professional journal of water industry,Water Wastewater Engineering(W WE)gained very wide acceptance from the colleagues working in this field in this country since start publication in 1964.Now it is administrated by the Ministry of Construction of the People’s Republic of China and sponsored by the China Civil Engineering Society etc. 相似文献
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解析法是库岸边坡地下水浸润线计算中便于实际应用的方法,但该方法须基于若干假定并对潜水运动基本方程线性化后才能求解。针对各假定和线性化过程建立不同的地下水渗流数学模型,用解析法和有限元法解答上述数学模型,分析各误差大小及其规律。结果表明:库岸垂直处理带来的误差要小于方程线性化处理和不考虑非饱和渗流带来的误差,而且它们都随渗透系数变大而减小;在三峡库区库水调度情况下,假定库水位等速变化带来的误差对大多岸坡而言可以忽略;计算库岸边坡地下水浸润线时,解析法只适用于水位变化幅度相比含水层厚度较小,且几何边界规则、岩土结构简单、岩土体渗透性较好时的情况。 相似文献
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Mutlu Ozdogan Curtis E. Woodcock Guido D. Salvucci Hüseyin Demir 《Water Resources Management》2006,20(3):467-488
Changes in summer irrigated cropland acreage and related water use are estimated from satellite remote sensing and ancillary
data in semi-arid Southeastern Turkey where traditionally dry agricultural lands are being rapidly transformed into irrigated
fields with the help of water from the Euphrates-Tigris Rivers. An image classification methodology based on thresholding
of Landsat NDVI images from the peak summer period reveals that the total area of summer irrigated crops has increased three-fold
(from 35,000 ha to over 100,000) in the Harran Plain between 1993 and 2002. Coupled analysis of annual irrigated crop area
from remote sensing and potential evapotranspiration based estimates of irrigation water requirements for cotton indicate
a corresponding increase in agricultural water use from about 370 million cubic meters to over one billion cubic meters, a
volume in accordance with the state estimates. These estimates have important implications for understanding the rapid changes
in current agricultural withdrawals in Southeastern Turkey and form a quantitative basis for exploring the changes in future
water demands in the region. For example, expansion of irrigated lands have led to a steady decrease in potential evaporation
due to increased roughness and decreased humidity deficit in the Harran Plain. Assuming that the changes in future evaporation
conditions will be of similar nature, water use for irrigation is expected to decrease over 40 percent in future irrigation
sites. Incorporating this decrease in overall planning of the irrigation projects currently under construction should lead
to improved management, and by extension, sustainability of water resources in the region. 相似文献
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用Vray三维渲染引擎来渲染三维场景,其质量和速度是由一些影响因素和参数设置决定的,不同的参数和因素,可以得出不同的三维渲染效果.因此,分析、优化三维渲染质量和速度的影响因素,正确、合理的选择参数对提高Vray最后渲染阶段的质量和速度非常重要. 相似文献
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本文从两相流体动力学的守恒方程出发,考虑固相、液相的相对运动,推导了可以考虑场的不均匀性和流体压缩性的统一形式的控制方程,并对方程所基于的物理概念和相互联系进行了必要的分析。通过对方程适当形式的表达,可导出用于大、小变形固结、渗流和沉积的简化方程,显示了在不同领域的三个理论存在一定的统一性。方程推导过程并未对本构关系加以限制,适用范围较广。依据实际问题的要求,作了不同形式的简化。 相似文献
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该文分析了四川省及重庆市几座中型水电站的调查材料表明:四川省及重庆市中型水电站不仅在川渝主网和地方电网中起着很大的作用,并具有巨大的社会效益,同时还有综合利用效益,说明修建中型水电站的优越性. 相似文献
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Reports concerning the influence of dams on river hydrology vary among researchers, interest groups and government agencies. These often contradicting statements may occur because changes in hydrology caused by dams are distinct for each dam and river watershed. The objective of this research was to use site specific techniques to determine if the 1967 installation of the Carlyle Dam, lower Kaskaskia River, Illinois, altered flood frequency and duration within the forested floodplain located below the dam. Results indicated a decrease in flood duration and frequency, and a decrease in annual flood frequency variation at a site 6.4 km below the dam. Pre‐dam versus post‐dam differences in flood frequency and duration at the site 32.2 km below the dam were related to climate rather than dam effects. Although dam impacts are a concern, this research shows that distance downstream from the dam and downstream tributary and watershed characteristics should be considered before assuming that the dam has changed hydrologic parameters for portions of rivers. This research also indicates that areas of the lower Kaskaskia River may still maintain hydrologic ecological integrity, and could be targeted for restoration and adaptive management purposes. Hydrologic modelling combined with river gage and on‐site well measurement techniques presented in this study could provide detailed flood frequency and duration information for land use, sociological and geomorphological questions in focus areas within river floodplains. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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Suitable thermal fish habitats are constrained by both maximum and minimum temperature tolerances. A multivariate and geostatistical approach was developed to estimate stream thermal characteristics at the river segment scale. Data from 22 temperature‐monitoring stations during summer 2007 were used to estimate monthly maximum temperature as well as thermal characteristics such as the number of events, the cumulative degree–days and the associated duration over specific temperature thresholds of 19 and 21°C. The probability of exceeding these temperature thresholds has also been interpolated. The methodology relies on the construction of a multivariate space using physiographic and hydrological characteristics of gauging stations as inputs in a canonical correlation analysis (CCA). A geostatistical interpolation technique, ordinary kriging, was subsequently used to perform interpolation in the physiographical space constructed using CCA. Results from this study were obtained for thermal characteristics estimated into two different interpolation spaces: (1) a 7 metrics space, and (2) an 8 metrics space. Cross‐validation technique has been performed and satisfactory results were obtained. Kriging thermal characteristics (magnitude and duration) into the 7 metric space for a 19°C threshold exceedance leads to best results with Relative Root Mean Square Error (RRMSE) ranging between 9.66 and 15.08%. The study shows that kriging in a multivariate space is a promising tool for water resources managers, especially in cases where risk mapping for lethal or sub‐lethal temperature thresholds may be required for a specific fish species. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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利用MgO膨胀剂的延迟微膨胀效应能显著提高大体积混凝土的力学性能,产生的预压应力还能有效提高大体积混凝土抵抗温度开裂的能力,但目前对其微观机理研究不多。采用宏观与微观相结合的方式,研究了不同活性指数、不同掺量的MgO混凝土的力学性能,利用SEM/EDS微观分析手段揭示了MgO对混凝土性能影响的作用机理。试验结果表明:MgO取代部分水泥掺入混凝土中,混凝土的力学性能降低;掺量为4%~5%时,活性指数为100s的MgO混凝土的膨胀率大于活性指数为50 s的MgO混凝土;MgO混凝土的膨胀特性与Ca,Si,Mg,Al等元素的分布情况有关,掺入的MgO将改变界面区Ca,Si,Mg元素的富集特性,Ca元素和Mg元素更易于在界面区富集,导致混凝土宏观力学性能的降低。 相似文献
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基于武汉地铁名都站深基坑工程与水文地质勘察资料,建立了三维工程地质仿真计算模型。依据名都站深基坑开挖支护方案,利用有限元软件MIDAS的摩尔-库仑本构模型,对武汉地铁名都站深基坑施工过程中,不同施工工序下每步开挖之后,基坑的变形情况做仿真模拟计算,并对比分析其对基坑稳定性的影响。结果表明:基坑围护结构的变形情况与施工工序有很大的关系,施工工序越合理,上部土体变形越小,反之越大。因此,在基坑工程的施工过程中,要注重施工步骤的划分与合理安排,从而保证基坑工程的安全。研究成果为以后武汉地区基坑工程的施工设计提供了值得借鉴的经验。 相似文献