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991.
Abstract Maximum observed floods (MOF) and their envelope curves are useful to hydrological engineers when estimating probable maximum floods or design floods. The World MOF and its envelope curve were developed originally in 1967 and modified in 2009 by our team. Based on MOF concepts and observed hydrological data in China, the China MOF and its envelope curve are presented, and their characteristics analysed. The results will be useful for flood design, for example for dam spillways, in China and in similar regions, in particular where no data are available, but cannot be used without modification and comparative analyses. Editor Z.W. Kundzewicz Citation Li, C., Wang, G., and Li, R., 2013. Maximum observed floods in China. Hydrological Sciences Journal, 58 (3), 728–735. 相似文献
992.
Abstract Reservoir silting is one of the principal problems affecting the performance of dams in Algeria from the standpoint of reservoir capacity for storage. Foum El Kherza Reservoir (also known as Foum El Gherza), near Biskra Town, Algeria, is subject to dredging operations with the intent of recovering 70% of its initial storage capacity of 47 hm3 (million cubic metres). The forecasting of sediment volume trapped in the reservoir is essential to plan the future use of this resource and to sustain irrigation for the palm groves characteristic of the region. However, there are currently no sediment data, nor a sediment rating curve, for predicting sediment inflow based on hydrological data. This paper describes the optimization of a cumulative trapped sediment curve for Foum El Kherza Reservoir based on 44 years of daily inflows, by using a spreadsheet optimization tool, Microsoft Excel® Solver to calibrate the cumulative sediment load against the cumulative sediment inflow as documented by eight bathymetric surveys since the dam construction. Editor D. Koutsoyiannis; Associate editor A. Montanari Citation Tebbi, F.Z., Dridi, H., and Morris, G.L., 2012. Optimization of cumulative trapped sediment curve for an arid zone reservoir: Foum El Kherza (Biskra, Algeria). Hydrological Sciences Journal, 57 (7), 1368–1377. 相似文献
993.
ABSTRACTWhen discharge measurements are not available, design of water structures relies on using frequency analysis of rainfall data and applying a rainfall–runoff model to estimate a hydrograph. The Soil Conservation Service (SCS) method estimates the design hydrograph first through a rainfall–runoff transformation and next by propagating runoff to the basin outlet via the SCS unit hydrograph (UH) method. The method uses two parameters, the Curve Number (CN) and the time of concentration (Tc). However, in data-scarce areas, the calibration of CN and Tc from nearby gauged watersheds is limited and subject to high uncertainties. Therefore, the inherent uncertainty/variability of the SCS parameters may have considerable ramifications on the safety of design. In this research, a reliability approach is used to evaluate the impact of incorporating the uncertainty of CN and Tc in flood design. The sensitivity of the probabilistic outcome against the uncertainty of input parameters is calculated using the First Order Reliability Method (FORM). The results of FORM are compared with the conventional SCS results, taking solely the uncertainty of the rainfall event. The relative importance of the uncertainty of the SCS parameters is also estimated. It is found that the conventional approach, used by many practitioners, might grossly underestimate the risk of failure of water structures, due to neglecting the probabilistic nature of the SCS parameters and especially the Curve Number. The most predominant factors against which the SCS-CN method is highly uncertain are when the average rainfall value is low (less than 20 mm) or its coefficient of variation is not significant (less than 0.5), i.e. when the resulting rainfall at the design return period is low. A case study is presented for Egypt using rainfall data and CN values driven from satellite information, to determine the regions of acceptance of the SCS-CN method.
EDITOR D. Koutsoyiannis; ASSOCIATE EDITOR A. Efstratiadis 相似文献
994.
《水文科学杂志》2013,58(3):556-570
Abstract Forest growth unfavourably reduces low flows and annual runoff in a basin in Japan. Annual precipitation and runoff of the watershed are summarized from observed daily rainfall and discharge, and annual evapotranspiration is estimated from the annual water balance. The water balance analysis shows obvious trends: reduced annual runoff and increased evapotranspiration over a 36-year period when forest growth increased the leaf area index. Between two periods, 1960–1969 and 1983–1992, mean annual runoff decreased 11%, from 1258 to 1118 mm, due to a 37% increase in evapotranspiration (precipitation minus runoff) from 464 to 637 mm. This increase in evapotranspiration cannot be attributed to changed evaporative demand, based on climatic variability over the 36-year period of record. Flow duration curves show reduced flows in response to forest growth. In particular, they suggest stronger absolute changes for higher flows but stronger proportional changes for medium and lower flows. A distributed model is applied to simulate the influences of five scenarios based on a 30% change in leaf area index and 5% change in soil storage capacity. From the simulation results, canopy growth appears to contribute much more to flow reduction than changes in soil storage capacity. 相似文献
995.
AbstractOne of the main challenges faced by hydrologists and water engineers is the estimation of variables needed for water resources planning and management in ungauged river basins. To this end, techniques for transposing information, such as hydrological regional analyses, are widely employed. A method is presented for regionalizing flow-duration curves (FDCs) in perennial, intermittent and ephemeral rivers, based on the extended Burr XII probability distribution. This distribution shows great flexibility to fit data, with accurate reproduction of flow extremes. The performance analysis showed that, in general, the regional models are able to synthesize FDCs in ungauged basins, with a few possible drawbacks in the application of the method to intermittent and ephemeral rivers. In addition to the regional models, we summarize the experience of using synthetic FDCs for the indirect calibration of the Rio Grande rainfall–runoff model parameters in ungauged basins.Editor D. KoutsoyiannisCitation Costa, V., Fernandes, W., and Naghettini, M., 2013. Regional models of flow-duration curves of perennial and intermittent streams and their use for calibrating the parameters of a rainfall–runoff model. Hydrological Sciences Journal, 59 (2), 262–277. 相似文献
996.
997.
三分量感应仪器最初的设计目的是测量薄交互层的电导率和层厚.建立0.3m三层和五层薄交互层模型,用COMSOL有限元软件三维数值计算三分量阵列感应8个水平线圈系子阵列响应,详细分析其响应特征与线圈间距和层厚的关系.结果表明,三层模型中的水平子阵列响应特征由其发射、屏蔽和接收在薄层中的位置决定,发射、屏蔽和接收进出薄层,在响应曲线上均有一定表现.当发射和主接收间距小于薄层厚度时,可有效分辨薄层.当发射和屏蔽之间的距离小于层厚时,可利用主接收进出薄层特征点识别薄层厚度.否则,由于发射、屏蔽和接收在层中的位置关系复杂和响应变化大,无法有效分辨薄层.此外,测井响应受围岩影响较大,读数不等于薄层的电导率.研究成果对三分量阵列感应仪器设计和测井响应解释评价具有重要的理论和实际意义. 相似文献
998.
At the mean annual scale, water availability of a basin is substantially determined by how much precipitation will be partitioned into evapotranspiration and run-off. The Budyko framework provides a simple but efficient tool to estimate precipitation partitioning at the basin scale. As one form of the Budyko framework, Fu's equation has been widely used to model long-term basin-scale water balance. The major difficulty in applications of Fu's equation is determining how to estimate the curve shape parameter ω efficiently. Previous studies have suggested that the parameter ω is closely related to the long-term vegetation coverage on large river basins globally. However, on small basins, the parameter ω is difficult to estimate due to the diversity of controlling factors. Here, we focused on the estimation of ω for small basins in China. We identified the major factors controlling the basin-specific (calibrated) ω from nine catchment attributes based on a dataset from 206 small basins (≤50,000 km2) across China. Next, we related the calibrated ω to the major factors controlling ω using two statistical models, that is, the multiple linear regression (MLR) model and artificial neural network (ANN) model. We compared and validated the two statistical models using an independent dataset of 80 small basins. The results indicated that in addition to vegetation, other landscape factors (e.g., topography and human activity) need to be considered to capture the variability of ω on small basins better. Contrary to previous findings reached on large basins worldwide, the basin-specific ω and remote sensing-based vegetation greenness index exhibit a significant negative correlation. Compared with the default ω value of 2.6 used in the Budyko curve method, the two statistical models significantly improved the mean annual ET simulations on validation basins by reducing the root mean square error from 114 mm/year to 74.5 mm/year for the MLR model and 70 mm/year for the ANN model. In comparison, the ANN model can provide a better ω estimation than the MLR model. 相似文献
999.
应变速率与单轴压缩强度极值的关系在抗冰结构设计与优化中占有重要地位。基于2009年冬季普兰店海域海冰在不同海冰温度(-5°C、-10°C、-15°C)下的压缩强度试验数据,给出各自应变速率—压缩强度散点图。结果表明,海冰在不同加载速率下表现为三种破坏模式,即韧性区、过渡区与脆性区;海冰温度对过渡区对应应变速率范围影响较小,均在6.3×10~(-4)~2×10~(-3)区域附近。结合三段式函数形式,给出不同温度下应变速率—压缩强度极值的曲线拟合结果。依据上述结论,在庄河海域选择应变速率10~(-2)、10~(-3)与10~(-4)进行不同海冰温度(-16°C~-4°C)下单轴压缩强度试验。结果显示:在韧性区,海冰温度与压缩强度极值呈弱负相关;在过渡区,海冰温度与压缩强度极值呈明显线性减小;在脆性区,强度极值相对海冰温度敏感度较低。基于此,在应变速率—压缩强度曲线中提出温度影响系数,这一试验分析方法可推广至其它海域。 相似文献
1000.
p-y 曲线法常用于水平静力受荷桩的分析，但海洋工程中的桩基除静力外还承受波、流等循环荷载作用，将静力 p-y曲线直接用于循环荷载下桩基的设计研究时，往往会产生误差。本文梳理了水平循环荷载作用下 p-y 曲线模型的研究成果，
按照得到循环 p-y 曲线的不同方式，将其分为总体调整法和参数修正法。在参数修正法中，根据修正时考虑的因素不同，分为考虑荷载特性的修正和考虑桩土相互作用的修正。最后通过对循环荷载作用下 p-y 曲线研究现状的总结对比，评价了不同方法的特点，讨论了当前研究存在的问题并给出了建议。 相似文献