水位降低时冰盖板对坝坡产生的弯矩计算分析

本文将冰盖板自重作为均布荷载，考虑了冰与坝坡冻结约束条件和冰的物理力学性质，建立了水位下降时，冰盖板对坝坡产生的破坏弯矩的计算公式。与现有国内外同类公式相比，该公式物理意义明确，参数易于确定，符合工程实际，便于工程应用。     

淮河蚌埠以下河道疏浚对降低洪水位的可行性及长效性研究

目前淮河中游洪涝灾害仍然严重,为了减轻灾害损失,迫切需要找到更加有效的治理措施。疏浚虽然是一种常用河道治理措施,可以理顺河势,降低洪水位,但是由于担心疏浚后回淤,效果不能维持,一直没有作为主要措施在淮河治理中使用。为此,首先从研究淮河中游河道演变规律出发,量化第二造床流量,揭示第二造床流量与平滩流量关系的机理,探寻淮河治理的新方法,为采用河道大规模疏浚来降低洪水位提供理论依据。然后采用非均匀不平衡输沙数学模型就上段疏浚、下段疏浚以及全河段疏浚对降低淮河干流洪水位的效果以及长期维持情况进行了计算研究。研究结果表明,长距离河道疏浚不仅能够大幅度地降低干流河道的洪水位,而且不会发生明显回淤,疏浚效果可以长期保留,为淮河的洪涝灾害治理提供了新思路和新措施。     

Monitoring models for base flow effect and daily variation of dam seepage elements considering time lag effect

Affected by external environmental factors and evolution of dam performance, dam seepage behavior shows nonlinear time-varying characteristics. In this study, to predict and evaluate the long-term development trend and short-term fluctuation of the dam seepage behavior, two monitoring models were developed, one for the base flow effect and one for daily variation of dam seepage elements. In the first model, to avoid the influence of the time lag effect on the evaluation of seepage variation with the time effect component of seepage elements, the base values of the seepage element and the reservoir water level were extracted using the wavelet multi-resolution analysis method, and the time effect component was separated by the established base flow effect monitoring model. For the development of the daily variation monitoring model for dam seepage elements, all the previous factors, of which the measured time series prior to the dam seepage element monitoring time may have certain influence on the monitored results, were considered. Those factors that were positively correlated with the analyzed seepage element were initially considered to be the support vector machine (SVM) model input factors, and then the SVM kernel function-based sensitivity analysis was performed to optimize the input factor set and establish the optimized daily variation SVM model. The efficiency and rationality of the two models were verified by case studies of the water level of two piezometric tubes buried under the slope of a concrete gravity dam. Sensitivity analysis of the optimized SVM model shows that the influences of the daily variation of the upstream reservoir water level and rainfall on the daily variation of piezometric tube water level are processes subject to normal distribution.     

Sea level variability in East China Sea and its response to ENSO

Sea level variability in the East China Sea (ECS) was examined based primarily on the analysis of TOPEX/Poseidon altimetry data and tide gauge data as well as numerical simulation with the Princeton ocean model (POM). It is concluded that the inter-annual sea level variation in the ECS is negatively correlated with the ENSO index, and that the impact is more apparent in the southern area than in the northern area. Both data analysis and numerical model results also show that the sea level was lower during the typical El Nio period of 1997 to 1998. El Nio also causes the decrease of the annual sea level variation range in the ECS. This phenomenon is especially evident in the southern ECS. The impacts of wind stress and ocean circulation on the sea level variation in the ECS are also discussed in this paper. It is found that the wind stress most strongly affecting the sea level was in the directions of 70o and 20o south of east, respectively, over the northern and southern areas of the ECS. The northwest wind is particularly strong when El Nio occurs, and sea water is transported southeastward, which lowers the sea level in the southern ECS. The sea level variation in the southern ECS is also significantly affected by the strengthening of the Kuroshio. During the strengthening period of the Kuroshio, the sea level in the ECS usually drops, while the sea level rises when the Kuroshio weakens.     

近断层脉冲型地震动作用下面板堆石坝的动力响应

越来越多的高土石坝正在西部地区建设或规划中,其中许多位于发震断裂带附近,遭遇近场强震的概率随着大坝数量的增加而增加,近断层脉冲型地震动作用下大坝地震响应特性亟待研究。本文选取10组台湾集集地震实测加速度时程,结合200 m级的面板堆石坝开展动力有限元分析,研究脉冲和非脉冲地震动作用对面板堆石坝的加速度、水平位移以及面板顺坡向应力的影响。结果表明,与非脉冲型地震动相比,脉冲型地震动对大坝堆石体的水平位移和面板顺坡向应力的影响较大,影响程度随着PGV/PGA(地面峰值速度/地面峰值加速度)的增大而增大。因此,在高地震区修建高土石坝时应对脉冲型地震进行专门研究,综合评价大坝的地震安全性和极限抗震能力。     

Fish assemblage response to recent mitigation of a channelized warmwater stream

Various designs of low‐head dams are used to rehabilitate streams or forestall upstream channel incision after channelization. We report on the efficacy of using notched sills and grade control structures (GCS) to restore the fish assemblage in Luxapallila Creek, Mississippi. We tested the null hypotheses that habitat variables and species richness, evenness, and assemblage structure would not differ among: (1) a channelized segment with no modifications; (2) a channelized segment mitigated by the installation of sills and GCS; (3) a segment upstream of the installations and undergoing channel incision; and (4) an unaltered segment. Although habitat variables changed, neither species richness, evenness, nor fish assemblage structure differed between mitigated and channelized segments with both exhibiting less richness and different assemblage structures than the unaltered segment. Lack of differences in species richness between the incised and unaltered segments suggest that the GCS may have halted the negative effects of upstream channel incision before species were extirpated. Conspicuous habitat differences between the altered (channelized and mitigated) and unaltered segments were lack of backwaters and canopy coverage and finer substrates in the altered segments. Our results suggest a more comprehensive rehabilitation strategy is required in Luxapallila Creek. Published in 2003 by John Wiley & Sons, Ltd.     

某水库实行汛限水位动态控制的探讨

为充分利用水资源,发挥防洪兴利效益,提出了某水库实行汛限水位动态控制的建议。从水库防洪安全泄量出发,基于预蓄预泄原理,推求汛限水位动态控制约束域,拟定符合实际情况的实施措施。实例计算和分析表明,水库实施汛限水位动态控制,可以解决兴利与防洪的矛盾,提高综合效益,为防汛调度决策者提供了参考依据。     

Monitoring access to water in rural areas based on the human right to water framework: a local level case study in Nicaragua

Much effort has gone into the recognition of the human right to water. Without doubt, this milestone influences governance and decision making processes at many scales so it is essential now to shift the discussion from the legal and conceptual framework to practice. Along this line, the article proposes a methodology for monitoring access to water in rural areas using the framework of this human right. The practicality of the approach is demonstrated by a case study carried out in Nicaragua. Different criteria of the right to water were included in surveys and structured interviews that were conducted in rural households and water committees, respectively. A discussion analyzes the advantages and challenges of using this framework. Finally, the approach provides elements for policy making that can be used by different stakeholders in the development and human rights sectors.     

Channel response to sediment replenishment in a large gravel‐bed river: The case of the Saint‐Sauveur dam in the Buëch River (Southern Alps,France)

The Saint‐Sauveur dam was built in 1992 in the middle section of the Buëch River. Downstream of the dam, a channel incision by several meters was observed. A gravel replenishment operation was planned in order to restore the active channel. An equivalent of two times the mean annual bedload‐transport capacity (43,500 m³) was replenished downstream of the dam in September 2016. The aim of this paper is to quantify morphological change associated with sediment remobilization in order to evaluate the efficiency of the restoration works. The monitoring was based on a combination of (a) change detection using sequential high‐resolution digital elevation models (from airborne LiDAR data), (b) bedload tracing using active ultrahigh‐frequency radio‐frequency identification technology, and (c) complementary field surveys of channel grain‐size distribution and morphology for bedload‐transport computation. Field monitoring allows us to capture a net aggradation along a 2‐km reach after the first post‐replenishment flood. A sediment balance analysis was performed to back‐calculate bedload supply coming from the sluicing operation during the flood. Although the sediment replenishment operation clearly had a positive impact on the morphological conditions of the starved river reach, the effective bedload supply from artificial berms (22,650 m³) was insufficient to initiate substantial channel shifting along the restored reach and a subsequent amplification of the sediment recharge. The combination of high‐resolution topographic resurveys and sediment tracing was successful to evaluate the downstream propagation of sediment replenishment effects.