摘要:

The Chezy friction formula for steady flow in a uniform symmetrical channel with constant slope-friction factor is examined mathematically. Firstly, a wide rectangular channel and a semi-circular channel are compared in respect of the mean flow velocity using the Chezy formula with the Manning, Chezy and logarithmic laws for velocity. Then the inverse Chezy problem, i.e. the determination of the channel shape above the reference level for a given depth/discharge rating curve, is posed and the differential-integral equation for its solution is derived. The rating curves used for computation are the results of multiplying the discharge for a trapezoidal shape above the reference level by an exponential function. To facilitate interpretation of the numerical results, the relationship between side slope and discharge is analysed. It is shown by the inverse problem solution that an exponential reduction of channel flow capacity changes linear channel sides into convex sides (making the cross section shape wider) while an exponential increase of capacity causes changes into concave sides (reducing a section width) which is against common sense.

ISSN:0262-6667    

DOI:10.1080/02626669609491537

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The Chezy formula for steady flow in a uniform symmetrical channel with constant slope-friction factor is mathematically examined. The problem of the determination of the channel shape above a reference level for a given rating curve of flow area vs discharge with a constant ratio (m) of slope to mean velocity above a reference level is posed and then solved. It is shown that there is a double solution of the problem. One solution (being of main interest) is unlimited and gives a shape widening with depth, while the other has an upper bound and yields a shape narrow-ing with depth. It is shown that a solution to the problem exists for a negative value of m. A relationship is examined between the width-to-depth ratio of a rectangular initial shape and a shape above a reference level for m values close to zero. In particular, the solutions for negative values of m, i.e. for discharge decreasing with increasing flow area, are evidently against common sense.

ISSN:0262-6667    

DOI:10.1080/02626669609491538

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The Saq aquifer is a Cambro-Ordovician Sandstone Formation that extends over 1200 km in Saudi Arabia and northwards in Jordan. It is an enormous groundwater reservoir where water is found under both unconfined and confined conditions. The main concern of this study was the quality of the Saq aquifer groundwater. This includes a description of the chemical composition of the groundwater, the spatial variation of its salinity and the processes that control this variability. A total of 384 wells drilled in the Saq aquifer were sampled and water analyses performed for the major ionic composition. The data were analysed using software computer programs. Saturation indices were calculated, ionic relationships were studied, hydrochemical facies were determined and water types were identified. The principal processes that control the groundwater quality variations are also discussed. The results of this study provide information needed for groundwater quality management in the Saq aquifer.

ISSN:0262-6667    

DOI:10.1080/02626669609491539

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Ranking of river basin planning and development alternatives under a multi-criterion environment, including both qualitative and quantitative aspects, is examined. The purpose is to find the most suitable planning for reservoirs with their associated purposes aimed at the development of the major peninsular river (Krishna) basin in India. A total of seven reservoirs and a diversion network are considered for the formulation of 24 alternative systems with 18 criteria, of which nine are qualitative and the remainder are quantitative in nature. A set of best alternatives with their ordering is obtained usingELECTRE(ELiminationEt (and)ChoiceTranslatingREality).

ISSN:0262-6667    

DOI:10.1080/02626669609491540

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This paper examines methodologies for the simulation of storms for the purpose of design flood generation in the Thames region. Existing methods are reviewed and two new approaches are proposed. One combines point profiles of storms extracted from long rainfall records with depth-duration-frequency statistics. The other uses a stochastic rainfall model based upon the Poisson point process to generate data. Rainfall events simulated by these two methods are compared and the flood statistics obtained by inputting these events into a rainfall-runoff model are examined for a small catchment in Surrey, England. The Poisson based model is recommended as the more reliable.

ISSN:0262-6667    

DOI:10.1080/02626669609491541

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Estimation of monthly runoff statistical properties, such as monthly means and variances, is usually needed to design and evaluate water resource systems. If no local recorded data are available, a transfer of information through different alternative procedures can be used. In this paper, the use of linear Transfer Function (TF) models with precipitation series as inputs is proposed to estimate statistical properties of the resulting runoff series. Empirical relationships based on data from watersheds in the mountainous zone of central Chile are suggested to estimate parameters of low-order TF models and some of their properties.

ISSN:0262-6667    

DOI:10.1080/02626669609491542

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Si le rôle des “surfaces saturées contributives” dans la formation des crues n'est plus mise en question sous climat tempéré, quand la végétation couvre convenablement les sols, la question de leur localisation demeure un problème important. Des travaux récents ont mis en évidence que d'autres facteurs peuvent avoir un rôle tout aussi fondamental que la topographie, souvent seule prise en compte. Ainsi, dans une région (Sud est du Brésil) où une érosion importante a précédé la phase de sédimentation responsable de la topographie actuelle, la paléotopographie est apparue comme un élément essentiel pour expliquer l'apparition des surfaces saturées. Par ailleurs, d'autres travaux montrent que les surfaces saturées ne sont pas toujours immédiatement connectées au drain principal, et que, alors, il n'est pas possible d'assimiler simplement “surfaces saturées” et “surfaces contributives à l'écoulement rapide de crue". Ces différentes observations concluent à l'importance de la compréhension du fonctionnement hydrologique des bassins versants avant de modéliser.

ISSN:0262-6667    

DOI:10.1080/02626669609491543

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Afin d'expliquer le fonctionnement de l'aquifère du karst du Moncayo, on a appliqué le modèle mathématique SIMERO aux 21 années pour lesquelles on avait les données du débit de la source. On a obtenu les valeurs pour le bilan d'une année moyenne: pluviométrie 714.2 mm; ruissellement 35.6 mm; évaporation réelle 404.9 mm; recharge 273.7 mm. A partir de ces résultats on a calculé les dépendances entre les valeurs de pluviométrie et de température avec la recharge, obtenant ainsi une courbe de régression. Le modèle SIMERO a été simplifié de telle façon que les débits de la source d'un mois déterminé puissent être calculés en connaissant seulement la précipitation et la température du mois étudié et le débit du mois antérieur.

ISSN:0262-6667    

DOI:10.1080/02626669609491544

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The sensitivities of groundwater-streamflow interaction to global climate change over the medium-sized mountainous Mesochora catchment in central Greece have been analysed. The global climate change was simulated through a set of hypothetical and monthly GISS (Goddard Institute for Space Studies) scenarios of temperature increases coupled with precipitation changes. The catchment hydrological regime, which is dominated by spring snowmelt runoff, was simulated by the coupling of the snowmelt and soil moisture accounting models of the US National Weather Service River Forecast System (US NWSRFS). The groundwater was represented through a lower zone one-tension water storage and two free water storages parameterized by the soil moisture model, while the streamflow was the sum of direct runoff, surface runoff and interflow from the upper zone free water, plus the primary and secondary baseflows yielded by the model. The interaction between groundwater and streamflow was expressed by the ratio of the two variables on a seasonal and monthly basis. Both representations of global climate change resulted in a moderate influence on the groundwater-streamflow interaction during the winter months and in a very high one in the spring and summer months. In particular, the major seasonal shift in the snow accumulation pattern related to climate change, as well as the large runoff reduction and evapotranspiration increase occurring in spring and summer months, boosted considerably the groundwater to streamflow ratio. This latter would probably have negative impacts on various problems of water resources management (e.g. droughts, water supply, irrigation, water pollution).

ISSN:0262-6667    

DOI:10.1080/02626669609491545

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This paper makes use of a water balance study of a mountainous area with a wide range of average annual rainfall in an arid and semiarid region to illustrate the development of both a statistical model of daily rainfall and a rainfall-runoff model. The models are appropriate for these conditions and may be relevant to similar areas. Comparisons of mean rainfall and runoff at the arid end of the scale suggest that runoff coefficients do not conform to common assumptions.

ISSN:0262-6667    

DOI:10.1080/02626669609491546

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor