摘要:

Two methods of estimating reforestation area for salinity control are described. The first method, a simple water balance model, has readily determinable parameters and sensitivity. Further parameter measurements are necessary to improve its reliability and applicability. The second method is based on regressions of observed water table reductions below reforestation on the area and density of reforestation. The regressions have high correlation coefficients and are statistically significant at the 0.1% level. A groundwater modelling approach to determine the optimum reforestation distribution was found to have extensive data requirements and involved assuming values for some key model parameters. Predictions should be checked in the field. The best current approach to reforestation design is to use the water balance model or experimental regressions to predict reforestation area, and then use the groundwater model to design the optimum reforestation layout.

ISSN:0262-6667    

DOI:10.1080/02626669009492401

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Soil and stream water aluminium and hydrogen ion data are presented for three Scottish catchments that are both acidic and acid sensitive. Stream waters have pH values ranging from 3.9 to 7.1 and aluminium concentrations in the range 0.07 to 129 μM 1−1. Within the soils H+concentrations decline with depth, being highest in the organic horizons and lowest in the inorganic horizons. Mean H+concentrations vary markedly from site to site (H+ranges from 12 to 111 and from 9 to 72 μM 1−1in the upper and lower soils respectively). Correspondingly dissolved aluminium varies with depth and from site to site (range from 2 to 21 and from 8 to 17 μM 1−1in the upper and lower soils respectively). Thermodynamic analysis of these data sets show that simple Al(OH)3and Al(OH)SO4solubility relationships are inoperative in the stream and soil zones. Dis-equilibrium “weathering” processes are inferred, even in the case where Al(OH)3(gibbsite) is found within the catchment.

ISSN:0262-6667    

DOI:10.1080/02626669009492402

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

L'essor considérable de l'exploitation des eaux souterraines en région soudano-sahélienne a rendu nécessaire d'évaluer l'alimentation naturelle des aquifères à partir des précipitations de pluie. Une recherche par un groupement international d'organismes a été réalisée en 10 sites regroupés en trois régions du Burkina-Faso. Chaque site a été équipé d'une station climatique et d'un dispositif de suivi en continu des niveaux de la nappe en 1985 et 1986 et a fait l'objet de pompages d'essai. Les données piézométriques de chaque site ont été analysées séparément par des modèles hydrologiques globaux pluie-ETP-ruissellement-recharge. La mise en oeuvre des modèles globaux a montré qu'en l'absence de mesures locales du ruisellement superficiel il n'est pas possible de les caler de manière unique compte tenu des difficultés d'évaluation du coefficient d'emmagasinement des aquifères. Une analyse des mesures de ruissellement superficiel dans des bassins voisins associée à une hypothèse d'homogénéïté des paramètres des modèles dans une même région a permis d'obtenir un calage unique qui constitue le meilleur compromis possible entre toutes les données. Une simulation des niveaux piézométriques de la période 1954–1986 et de la recharge, à partir des relevés piézométriques disponibles en 4 stations synoptiques, a permis d'évaluer la variabilité de la recharge et de situer statistiquement la période d'observation de 1985–1986. La recharge annuelle calculée varie d'une année à l'autre dans un rapport 1 à 2 ou 1 à 3 selon le site. La simulation fait apparaître que la recharge calculée en 1985 est proche du minimum de la période 1954–1986 dans les régions de Katchari, Silmissin et Barogo et proche de la moyenne dans la région de Sideradougou.

ISSN:0262-6667    

DOI:10.1080/02626669009492403

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The linear flood routing model presented has been derived from the linearized St. Venant equation for the case of a uniform open channel with arbitrary cross-sectional shape and friction law. In order to filter out the downstream boundary condition the kinematic wave solution is used to approximate the diffusion term in the St. Venant equation. The hydrodynamic model obtained is called the rapid flow model (RFM). It provides the exact solution for a Froude number equal to one. Such characteristics of the RFM impulse response as cumulants, amplitude and phase spectra are analysed, and then compared with those of the complete linearized St. Venant equations for different reach lengths, values of Froude number and frequencies of flood waves. The RFM can be applied for mountainous rivers that have large Froude numbers and both quick and slow rising waves.

ISSN:0262-6667    

DOI:10.1080/02626669009492404

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A gap between hydrodynamic modelling and conceptual modelling of flood routing has been filled by the introduction of conceptual elements. The conceptual model gives results equivalent to those of the complete linearized Saint Venant equations for Froude number equal to one and approximately so in that vicinity. It has been applied to the case of a uniform open channel with arbitrary cross section and friction law. Pure lag has been introduced to the Muskingum model and then such models with physically based parameters have been coupled in series forming a multiply delayed Muskingum model. The asymptotic case when, for a finite river reach, the number of submodels tends to infinity, gives the distributed delayed Muskingum model. Further, this model is a particular solution of the complete linearized Saint Venant equations known as the rapid flow model. The model not only originates from conceptual elements but its impulse response has a clear conceptual interpretation.

ISSN:0262-6667    

DOI:10.1080/02626669009492405

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The paper evaluates the performance of a non-parametric scheme, the nearest neighbour (NN) method, to predict the daily mean discharge in a mountain basin supplying a hydroelectric reservoir in northeastern Italy. The results are compared with those of an autoregressive model with exogenous input (ARX), coupled with a previously developed snow cover evolution model. Both methods give good performances, but the NN prediction requires a much simpler simulation structure. In the case investigated, for example, the snowpack accumulation-melting model can be completely eliminated. This greater simplification assumes considerable importance in the Electric Load Distribution Institutes of the Italian National Electricity Board (ENEL), where many hydroelectric basins are managed every day.

ISSN:0262-6667    

DOI:10.1080/02626669009492406

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626669009492407

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626669009492408

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626669009492409

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626669009492410

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor