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91.
Limitations of real-time models for forecasting river flooding from monsoon rainfall 总被引:1,自引:0,他引:1
Very intense rainfall during the southwest and northeast monsoons causes severe river flooding in India. Some traditional
techniques used for real-time forecasting of flooding involve the relationship between effective rainfall and direct surface
runoff, which simplifies the complex interactions between rainfall and runoff processes. There are, however, serious problems
in deducing these variables in real time, so it is highly desirable to have a real-time flood forecasting model that would
directly relate the observed discharge hydrograph to the observed rainfall. The storage routing model described by Baba and
Hoshi (1997), Tanaka et al. (1997), and Baba et al. (2000), and a simplified version of this model, have been used to compute observed river discharge directly from observed hourly
rainfall. This method has been used to study rainfall–runoff data of the Ajay River Basin in eastern India. Five intense rainfall
events of this basin were studied. Our results showed that the Nash–Sutcliffe efficiency of discharge prediction for these
five events was 98.6%, 94.3%, 86.9%, 85.6%, and 67%. The hindcast for the first two events is regarded as completely satisfactory
whereas for the next two events it is deemed reasonable and for the fifth it is unsatisfactory. It seems the models will yield
accurate hindcast if the rainfall is uniform over the drainage basin. When the rainfall is not uniform the performance of
the model is unsatisfactory. In future this problem can, in principle, be corrected by using a weighted amount if rainfall
is based upon multiple rain-gauge observations over the drainage basin. This would provide some measure of the dispersion
in the rainfall. The model also seems unable to simulate flooding events with multiple peaks. 相似文献
92.
Three cores from two connected lakes in Central Ireland (Lough Kinale and Derragh Lough) were investigated using diatom analysis
to establish the Holocene development of the lacustrine system, any local variations within the lakes and any anthropogenic
influences. The study area was situated in a lowland location and the lakes were shallow, unstratified and interconnected.
Litho-and bio-stratigraphical analyses of the lake cores and deposits beneath a mire separating the two lakes showed the changing
spatial configuration of the lake system in the early Holocene and the separation of the initial lake into three basins (cf.
lacustrine cells) and finally into two interlinked lakes. The evolution of the lake system is conceptualised as the development
of distinct lacustrine cells, and its sediments have recorded changes in the physical (geography, depth and sedimentation)
and chemical (water chemistry) properties of the lakes inferred through diatom analyses. The longest sequence, from the early
Holocene, records fluctuating lake levels and these are correlated with geomorphological mapping and surveying of palaeoshorelines.
The diatom assemblages of the upper 2 m of the three cores, covering approximately the last 2000–3000 radiocarbon years show
considerable difference in trophic status and life-form categories. This is related to the location of the cores in the lake
and also the distance from human settlement with particular reference to proximity to crannog (artificial island) construction
and use. The most central core from the deepest part of Lough Kinale has the least representation of the human settlement
and agricultural activity in the catchment and on the fringes of the lake, whereas the core taken from the edge of a crannog
is able to identify when construction and use of the crannog occurred. The local nature of the palaeoecological response to
human activity due to incomplete water mixing has the advantage of allowing the lake sediment cores to be used to determine
spatially discrete settlement patterns. 相似文献
93.
94.
90年代长江中游异常多雨的气候变化背景分析 总被引:9,自引:1,他引:9
利用小波变换技术, 对与长江中游地区夏季降水密切相关的赤道东太平洋海温、西太平洋副高、南海夏季风等物理因子进行时间变化的尺度分离.通过对年代际变化和长期趋势等不同尺度变化的分析, 揭示出90年代长江中游异常多雨和频繁洪涝产生的气候变化背景. 相似文献
95.
利用Fourier Bessel级数展开法,给出了表面具有覆盖层的圆弧形凹陷地形对入射平面SV波散射问题的一个解析解,并利用该解分析了不同深宽比凹陷地形表面覆盖层刚度和厚度对入射SV波的影响.结果表明,凹陷地形表面覆盖层的存在,即使厚度很薄,也会显著增加对入射SV波的放大作用,该放大作用可达到单一凹陷地形的2.5倍以上.覆盖层刚度和厚度的变化对入射平面SV波也具有很大影响. 相似文献
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100.
In order to realize sustainable development of the arid area of Northwest China, rational water resources exploitation and optimization are primary prerequisites. Based on the essential principle of sustainable development, this paper puts forward a general idea on water resources optimization and eco-environmental protection in Qaidam Basin, and identifies the competitive multiple targets of water resources optimization. By some qualitative methods such as Input-output Model & AHP Model and some quantitative methods such as System Dynamics Model & Produce Function Model, some standard plans of water resources optimization come into being. According to the Multiple Targets Decision by the Closest Value Model, the best plan of water resources optimization, eco-environmental protection and sustainable development in Qaidam Basin is finally decided. 相似文献