摘要:

Systematic measurements of the longitudinal dispersion coefficient, DL, were made in 10 different soil samples. Four samples consisted of uniform grains and six non-uniform, composed by mixing the uniform samples. Tests yielded a linear relationship between DLand the seepage velocity, u, for both uniform and non-uniform samples. The process of dispersion, however, has a complex character in non-uniform media, particularly in samples with a discontinuous grain-size distribution curve. In such cases the value of DLmay increase up to the value of DLfor the coarser-grained component depending on the deviation of the average grain size of the individual components. These irregular dispersion properties probably arise from the irregular pore-size distribution of the non-uniform samples.

ISSN:0262-6667    

DOI:10.1080/02626668609491067

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

In developing countries, the use of mathematical models in hydrological forecasting is increasing, making for optimal planning and management of water resources systems. Such application, however, faces different problems. One of these problems is that computers may not be available. Even if they are available, computer time is expensive. Hence, there is a need for simple models which can be run on pocket calculators or which are computer-time efficient, with high accuracy. This paper presents a rainfall-runoff model with a very simple structure. With simple algorithms, the model can be used with computers with small memory capacity. A method for estimating mean areal rainfall, representing the detailed distribution of rain over an area, is also put forward. The model has been applied to a small, mainly rural catchment in northern Tunisia for both single rainfall event simulation and continuous simulation for longer periods. The outcome was most encouraging. In the present paper the measured and calculated streamflows are presented and discussed.

ISSN:0262-6667    

DOI:10.1080/02626668609491068

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Lateral subsurface flow within a 10% forested slope in a part of the humid tropics of southwestern Nigeria during 1982 is described with particular regard to the cumulative amount, timing and frequency of seepage, the relative contributions of the various soil horizons to the total seepage, and factors affecting these seepage parameters. Seepage was collected at 30, 500, 900, 1200 and 1800 mm depths by means of troughs connected to plastic collectors, and measurements were made between March and November 1982. The total amount of seepage during the study year was 67.7 mm and this was obtained from a total of 29 seepage days. This is considered low given the number of rainy days (106), the total rainfall for this period (924 mm) and results from other environments. The impeding layer in the soil is within the 900–1200 mm horizon, but the largest relative contribution to total seepage was not from the horizon immediately above this layer (i.e. 500–900 mm), but from the surface 0–30 mm horizon. Soil moisture status and hydraulic conductivity as influenced by the rainfall pattern were found to be very important in controlling the seepage patterns.

ISSN:0262-6667    

DOI:10.1080/02626668609491069

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

For the purposes of this paper, water resources management is defined in its broadest terms and deemed to encompass all water-related aspects of river-basin management from long-term planning through to real-time operational control. Bearing in mind the increasing pressure on finite resources, an integrated, multifunctional approach is advocated in which different analytical procedures are used at various stages of decision making. These include mathematical programming, large-scale simulation and optimal control theory. By way of example, the application of these techniques to water resources in the United Kingdom is briefly described.

ISSN:0262-6667    

DOI:10.1080/02626668609491070

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Assistance to developing nations in the area of water resources has shown mixed successes and failures. A major factor is the capacity of the receiving nations to make good use of the resources provided at their stage of development—their “absorptive capacity”. Programmes must be tailored to the situations. This requires planning that is specific to the national and cultural context, as well as careful sensitivity to positive interaction with those who will be expected to implement programmes whose real purpose should be to allow the entire population, especially its very poor, to become socially effective and self-aware as well as more productive and comfortable. It also requires careful preparation in the way of education, science and institutional responsiveness. Experts and government leaders must reconsider their approaches to the problems so that the nations can learn and think for themselves.

ISSN:0262-6667    

DOI:10.1080/02626668609491071

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The temporal variations of spring water chemistry are used to support observations on the nature of groundwater circulation inside a karstified carbonate terrain. Variations in some hydrochemical properties such as the Ca++/Mg++ratio, the hardness, the electric conductivity, the CO2partial pressure, and the calcite and dolomite saturation ratios are used to give indications with regard to the nature of the carbonate rock, the groundwater residence time, and the mode of water circulation inside the karstic system. The seasonal variations of these properties during four years of monitoring were determined for six adjacent springs in a karstified carbonate terrain in northwest Iraq. The carbonate terrain, which is known to be mostly limestone with some dolomitic limestone beds, has given an average value of 3.3 for the Ca++/Mg++ratio. The magnesium and calcium hardness has high values (341–368 ppm) with a coefficient of variation that exceeds 11%. The PCO2has a minimum of 10−2.7bar and a maximum of 10−1.8bar. The values of the calcite and dolomite saturation indices fluctuate about saturation levels in spite of the presence of an appreciable concentration of NaCl. These results, when combined with other analyses and observations related to the flow rate characteristics of the springs, have revealed that the six springs are fed by a common diffuse type karstic system with a rather high but acceptable coefficient of variation of hardness.

ISSN:0262-6667    

DOI:10.1080/02626668609491072

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The paper presents the observed effects on the streamflow of changing a tropical forest in the high rainfall belt of Zambia to agricultural use based on traditional farming methods. Hydrological observations were carried out on four small catchments under their natural conditions first, and later two of them under agricultural use with accompanying deforestation. Simple linear regression analysis of both monthly and annual runoff from the treated catchments on the monthly and annual runoff from undisturbed catchments showed that there was an increase in streamflow as a result of deforestation and subsistence agriculture. It is also shown that the shape of the flood hydrograph was changed as a result of changes in land use.

ISSN:0262-6667    

DOI:10.1080/02626668609491073

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626668609491074

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626668609491075

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626668609491076

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor