从两次洪水分析中看非工程措施对防洪的影响

本文通过对赣江流域袁河“82·6”和“89·7”两次大洪水的分析比较,得出结论:准确的水情预报和水库工程正确的调度方式,能减轻下游防洪负担,最大限度地减少洪灾损失,夺取抗洪斗争的胜利。文中提醒人们,在防汛工作中,应把非工程措施提高到相当的地位来加以重视。     

An approach to the synthesis of qualitative ecological information from aquatic coleoptera communities

A list of 196 Coleoptera taxa, larvae and adults, covering 113 species, was obtained from several surveys of a flood plain of the Rhô river. From published reports and personal experience, each taxon is linked with the modalities of nine environmental and three biological variables. The resulting 12 ecological profiles for 196 taxa are analysed by correspondence analysis. The simultaneous ordination of the taxa and variables allows presentation of the more synthetic correspondence between the Coleoptera and their ecological and biological characteristics. The niche dimensions of the 12 variables tested here are organized along a current-substrate gradient, from stones in rapid flow to mud in still water, which is associated with the other ecological conditions. This ordination reflects environmental conditions in a transverse direction, particularly from the central channel to the furthest annexes of the river. The Coleoptera are shown to be describers of the connectivity with the main channel. The 196 studied taxa are positioned along the gradient. They are subdivided into seven faunal groups based on their habitat range or niche width. The larger species are confined to the stagnant side of the gradient. Other variables, such as feeding and vertical distribution, clearly separate carnivores from herbivores and also larvae from adults. The next step of this study will be to extend these investigations to other functional variables and to all the species of Coleoptera in France. The information given by the Coleoptera will then be compared with actual field measurements.     

The Installation and Use of a Snow Pillow to Monitor Snow Water Equivalent

In February 1993, a snow pillow was installed at Widdibank Fell near Cow Green reservoir (in Upper Teesdale) to monitor snow water equivalent.
This paper describes existing snow-measurement techniques in the UK and the site-selection process and installation details for the snow pillow. Following a winter of more than 100 days with snow cover at the site, the success of the pillow in representing site and catchment snow conditions and in providing operationally useful snowmelt information for flood warning has been assessed.     

Polychlorinated biphenyls (PCBs) in sediments of the southern Baltic Sea — trends and fate

Polychlorinated biphenyls (PCBs) have been determined in recent [0–1(2), 1(2)–5 and 5–10 cm deep layers] sediments from different sites of the southern Baltic Sea, including the Szczecin Lagoon, collected from May 1996 to October 1999, i.e. before and after the great flood in Poland of July/August 1997. The PCB distribution has been correlated with location and hydrological conditions as well as with organic carbon, algal pigments and their derivatives in the sediments. The sum of PCB (seven congeners) was equal to 1–149 ng/g dry wt., on average this was rather low (up to 40 ng/g). There was a decreasing trend in PCBs concentrations in the bottom sediments of the southern Baltic in 1996 but considerable amounts were still accumulated there. The flood of 1997 caused a distinct increase of PCB concentration level in the sediments, which again showed a decreasing trend in the next few years. This illustrates that at present the main source of PCBs for the southern Baltic are not a direct consequence of human activity, but from floods and heavy rains washing these compounds from land to the sea. Algae and algal detritus play an important role in the transport and distribution of PCBs in the southern Baltic. High correlation of PCBs with chlorophyll a derivatives — products of zooplankton grazing — indicates that PCBs are ingested by zooplankton with phytoplankton and then exuded with fecal pellets. PCBs bound to algal detritus or to fecal pellets in the water column are transferred to sediments, there they may be trapped either in a bonded and unchanged form or resuspended, remobilized and/or dechlorinated, depending on their properties and environmental conditions.     

洪水水文预报系统

水文预报系统是计算机算法应用于水文预报的一次实践 ,在从产汇流原理出发 ,详细阐述系统结构 ,工作原理及系统特征 ,还对软件的应用及今后开发前景进行了展望 ,随着社会发展和科技进步 ,实施计算机预报系统便于提高预报精度 ,增强水文预报的时效性 ,将使水文预报作用日益显著。     

应急通信演练规程探讨

就应急通信演练规程中应注意的问题作了简要阐述和总结，并对应急通信机车运行、传输实施、基站开通提出了一些建议。     

Flood Plain Filling by a Monoclinal Flood Wave

Theoretical equations are derived to estimate the flood wave celerity and the volume of lateral flow leaving the main channel and entering the flood plain for a two-dimensional monoclinal wave. The equations are based on conservation of water mass assuming an idealized compound channel. The parameters that affect the lateral flow volume are the ratio of flood plain depth to the depth in the main channel at the peak discharge, the ratio of the flood plain width to the main channel width, and the ratio of the flood plain roughness to the main channel roughness. The percentage of flood plain volume filled up by lateral flow from the main channel increases as the width ratio decreases, the roughness ratio increases, or as the depth ratio decreases.     

Information Theory and Neural Networks for Managing Uncertainty in Flood Routing

This paper presents an approach for handling uncertainties arising mainly from ignored or misrepresented processes in physically based models. The approach is based on the application of a parallel artificial neural network (ANN) model that uses state variables, input and output data, and previous model errors at specific time steps to predict the errors of a physically based model. Concepts from information theory are used to discover the relationships between the variables and the model errors, which also serves as a mechanism to detect the predictability of the errors. The resulting information is used to select the best related input data for the error prediction model. The error prediction model is then trained and applied to improve the forecasts made by the physically based model. This approach was applied to a routing model of a 70 km reach of the River Wye, United Kingdom. The results demonstrate that errors from the physically based model show a consistent trend governed by some dynamics of their own, which can be modeled with learning algorithms. Errors were forecasted at different lead times. In all cases the forecasts made by the combined application of both models were more accurate than those made by the physically based model alone. From this it was concluded that, along with proper information analysis techniques, the use of ANN models to predict the forecast errors of physically based models can help to improve significantly the prediction and therefore to reduce the associated uncertainty.     

HSPF Simulation of Runoff and Sediment Loads in the Upper Changjiang River Basin, China

To evaluate the performance of a computer model simulating runoff and sediment load in the upper region of the Changjiang (Yangtze River) basin over a relatively short time interval, including examining the applicability of the input precipitation data generated from global circulation models and satellite data, we used a spatially distributed model, HSPF with the International Satellite Land Surface Climatology Project (ISLSCP) precipitation data for 1987 and 1988 as input data. The Nash–Sutcliffe coefficient (R2) for 5-day average streamflow was 0.94 in the calibration period and 0.95 in the verification period for the whole upper region. Moreover, the model simulated the 5-day average streamflow well in each main tributary, as shown by R2 values of 0.46–0.96, except that it underestimated the peak flow rates during the flood season over 2 years by up to 71% in Tuojiang and 61% in Jialingjiang. The model simulated the 5-day concentrations of suspended solids (SS) fairly well in the headwaters and upper regions of the Jinshajiang, Yalongjiang, and Minjiang watersheds, as shown by R2 values of 0.31–0.65. In the other regions, however, the model underestimated the SS load by up to 72%, and rarely simulated the fluctuation of SS concentration in each river channel during the flood season. These errors led to the underestimation of sediment runoff volume from the whole upper region during the flood season, as shown by the ratio of the simulated sediment load to the observed data at Yichang: 0.69 in the calibration period and 0.68 in the verification period. The ISLSCP precipitation tended to be more frequent and less intense than the measured precipitation. This was probably the main reason why the HSPF did not perform well in all regions at all times.     

Treatment of Natural Geometry in Finite Volume River Flow Computations

A method is proposed for the treatment of irregular bathymetry in one-dimensional finite volume computations of open-channel flow. The strategy adopted is based on a reformulation of the Saint-Venant equations. In contrast with the usual treatment of topography effects as source terms, the method accounts for slope and nonprismaticity by modifying the momentum flux. This makes it possible to precisely balance the hydrostatic pressure contributions associated with variations in valley geometry. The characteristic method is applied to the revised equations, yielding topographic corrections to the numerical fluxes of an upwind scheme. Further adaptations endow the scheme with an ability to capture transcritical sections and wetting fronts in channels of abrupt topography. To test the approach, the scheme is first applied to idealized benchmark problems. The method is then used to route a severe flood through a complex river system: the Tanshui in Northern Taiwan. Computational results compare favorably with gauge records. Discrepancies in water stage represent no more than a fraction of the magnitude of typical bathymetry variations.