摘要:

A time-dependent modified Fickian type model in which the longitudinal dispersion process is considered as consisting of three stages is presented. The first stage is for t/t0⩽ 0.1, the second stage is for 0.1 < t/t0< 20, and the third stage is for t/t0⩾ 20. The Lagrangian time scale t0used here for longitudinal dispersion is considered as different from the corresponding t0defined for diffusion. The approach has both theoretical as well as empirical bases. Calibration of the first stage of the model has been carried out using laboratory data. Satisfactory predictions have been obtained for a limited range of data.

ISSN:0262-6667    

DOI:10.1080/02626668309491988

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

A time-dependent dispersion model based on Lagrangian correlation and calibrated using laboratory data is applied to predict dispersion in four narrow streams in Hong Kong. For early stages of dispersion, the model parameters were completely known from laboratory results. For large times, the Lagrangian time scale t0for dispersion was estimated by a trial and error procedure. Satisfactory predictions have been obtained for the test reaches considered.

ISSN:0262-6667    

DOI:10.1080/02626668309491989

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

A monthly conceptual rainfall—runoff model that enjoys fairly widespread use in South Africa was calibrated for each of 50 calibration samples of lengths 3–20 years, drawn from a synthetic 101-year semiarid streamflow time series generated with the Stanford Watershed Model. The ability of Pitman's model to reconstruct the original 101 years of monthly streamflow for each of the 50 calibrations was then examined against a set of statistics of monthly and annual streamflows. The variabilities of key model parameters associated with different lengths of calibration period were also investigated. The results show that it is well worthwhile to increase the calibration period to about 15 years in order to reduce errors in reconstructed flow statistics. Merely increasing the length of calibration period from 6 to 10 years may decrease the error in most regenerated flow statistics by 30–50%. A fair amount of variability in “optimum” parameters, however, seems unavoidable, even at longer calibration periods, though this may also partly be due to imperfect model calibration. The effects of this variability are greatly attenuated in the reconstructed flow statistics due to parameter interdependence.

ISSN:0262-6667    

DOI:10.1080/02626668309491990

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The paper presents a method of determination of areal value of degree-day factor by plotting basin snowmelt against the degree-day multiplied by the area of snow cover; some studies regarding stability of this degree-day factor are also presented. The question of open patches inside the snow cover poses difficult problems in conceptual modelling of snowmelt runoff. Some ignore it, others measure snow cover patch by patch. The paper suggests some ways of reconciling these two approaches.

ISSN:0262-6667    

DOI:10.1080/02626668309491991

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Flow discharge measurements during floods are of considerable importance. These data are very valuable and particularly difficult to obtain. In addition, such measurements are very expensive and often the lives of the people carrying them out are endangered. The paper describes several methods of discharge measurements during floods. It also presents some practical experience with the following types of measurements as variants of the moving boat method: discharge measurements of the whole flood wave using one or two boats employing only the current meter; and the rising floats of different rise speed.

ISSN:0262-6667    

DOI:10.1080/02626668309491992

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Recharge to phreatic aquifers in the Deccan Trap basalt formation due to 1980 precipitation was determined in the Kukadi and Godavari-Purna basins by tritium injection. Tritium was injected in June 1980, just before the onset of monsoon, at a depth of 60 cm; vertical soil profiles were collected after the monsoon and also at the end of the hydrological year, i. e. in May 1981. Laboratory measurements of variation in moisture percentage and tritium concentration with depth were used in estimation of recharge. Recharge values for 19 sites in Kukadi basin varied from 135 to −8mm while those for 24 sites in Godavari-Purna basin varied from 208 to −28 mm, giving mean values as 46 and 56 mm respectively. Annual input to the groundwater reserves of the two basins was calculated as 31.9 and 35.4 million m3respectively. A qualitative correlation between recharge values and water level fluctuation data for dug wells was observed and a reasonable agreement with hydrogeological estimates of recharge was also found. The effect of evaporation in dry summer months on moisture in the deep percolation zone was evaluated through comparison of post-monsoon 1980 and pre-monsoon 1981 recharge values.

ISSN:0262-6667    

DOI:10.1080/02626668309491993

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The different factors that produce evaporation of moisture from a capillary porous medium are being investigated. Thermodynamic measurements of the porous medium-air-water system and a mathematical model have permitted the establishment of some correlations between the principal non-dimensional numbers associated with heat and mass transfer between the evaporating water in the porous medium and the external gas stream. These correlations lead to the prediction of some important parameters such as the depth of the surface of vaporization and the exchange coefficients of the heat and mass transfer during the evaporation from a capillary porous medium.

ISSN:0262-6667    

DOI:10.1080/02626668309491994

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626668309491995

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626668309491996

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626668309491997

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor