摘要:

Fresh groundwater within the Plymouth Limestone can be shown to be in hydraulic continuity with the marine waters of Plymouth Sound. Fresh groundwater discharges from the limestone in the form of submarine springs can be detected on the basis of temperature differences between the fresh groundwater and the marine waters, using an aircraft-mounted thermal infrared linescanner. Analysis of the thermal data is improved and aided by the use of the GEMS colour contouring analysis facility.

ISSN:0262-6667    

DOI:10.1080/02626668509490983

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The efficient management of an agricultural system or the operation of a water supply scheme requires knowledge about critical droughts, such as their length, severity and frequency of occurrence. Several theoretical distributions are fitted to drought events of up to one year's duration and the average recurrence intervals calculated. A methodology based on stochastically generated data is proposed and used to obtain the average recurrence intervals of events of duration longer than one year. These methods are applied to five river basins in Victoria. The accuracy of the method is dependent on the adequacy of the generating model.

ISSN:0262-6667    

DOI:10.1080/02626668509490984

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

A critical review of earlier uses of bomb tritium spotlights problems in its applications that may result in erroneous interpretations. The old monitoring technique using boreholes causes mixing of groundwaters of different age zones. In this study, the mixing problem is overcome by using modern monitoring devices of multi-level samplers and bundle piezometers that yield groundwater samples of small volumes at closely-spaced intervals. The old method may be used to determine recharge and discharge areas of aquifers and used where pollution poses no serious threat. Otherwise, the major pumpage of the aquifer distorts and reverses flow directions, causes mixing of different waters and may spread the pollutants. The disadvantages of the modern method include its restricted use in shallow aquifers and porous media.

ISSN:0262-6667    

DOI:10.1080/02626668509490985

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Because of significant physical differences between snow and other naturally occurring substances, snow is not only a valuable resource but it also has significant large-scale effects on weather, climate and the hydrological cycle. A working group of the IAHS International Commission on Snow and Ice (ICSI) has recently reached certain conclusions regarding these effects. In order to study and model the large-scale effects of snow, the standardization of existing ground observation methods, the exploitation of new technologies such as remote sensing, and the systematic archiving of all data are necessary. Various research efforts and international activities have been identified which, when accomplished, should lead to improved understanding and management of the large-scale effects of seasonal snow cover. An international organization should take the lead in promoting an exchange of ideas, techniques, measurements, research results and management strategies on large-scale snow studies.

ISSN:0262-6667    

DOI:10.1080/02626668509490986

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

This paper reviews the magnitude of soil erosion in tropical Africa and relates it to erodibility, erosivity and landform in different ecological regions There are few direct measurements of erosivity and erodibility in tropical Africa and the relevance of using the Universal Soil Loss Equation in estimating these parameters is reviewed. Soil erodibility is not a fixed parameter and changes with time. Although localized rates of soil erosion can be high, the erosion rates derived from sediment loads in rivers are often low. Most of the available data on sediment loads of African rivers are 10–20 years old, and little research information is available on the delivery ratios associated with different catchments. Rapidly changing land use is one of the major factors responsible for accelerated soil erosion, and the effects of deforestation, grazing, fire, and of cultural practices are discussed. The economics of soil erosion is reviewed in terms of loss in productivity and siltation of reservoirs. Research and development needs are listed.

ISSN:0262-6667    

DOI:10.1080/02626668509490987

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The distribution of permeability and chemical character of groundwater in carbonate aquifers is significantly influenced by the many diagenetic processes and reactions that occur in the early development of these rocks. Many of these diagenetic processes occur in the transition zone formed as the carbonate sediments emerge from the marine environment and become fresh-water aquifers. Analyses of trace elements and isotopes indicate that calcite cements and dolomites are formed in this groundwater mixing zone. Reverse reactions such as mineral dissolution and dedolomitization occur in carbonate aquifer systems. The geochemical reactivity of the fresh-water/salt-water mixing zone results from the nonlinearity of geochemical parameters as a function of ionic strength and causes extensive dissolution in coastal carbonate rocks. Interpretation of geochemical reactions and isotopic composition of groundwater provides a method to determine hydrological parameters such as porosity, hydraulic conductivity, and groundwater flow rates. This geochemical method is largely independent of the more conventional approach of determining these parameters by an evaluation of physical properties of aquifer systems.

ISSN:0262-6667    

DOI:10.1080/02626668509490988

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The probability-distributed principle in basin-scale hydrology considers the frequency of occurrence of hydrological variables (model inputs, parameters or elements) of certain magnitudes over the basin without regard to the location of a particular occurrence within the basin. The random assemblage of different parts is considered more important than the relation of the parts, one to another. Rainfall-runoff models based on probability-distributed infiltration capacity and storage capacity concepts, and which generate runoff according to Hortonian and saturation overland flow mechanisms respectively, are distinguished. Two types of probability-distributed storage capacity model are identified, one based on an assumption that storage elements at points in the basin respond independently of their neighbours, and the other where storage elements interact so as to equalize the depth of stored water over the basin. Allowing redistribution of water leads to simplification of the model equations. The probability-distributed principle is also used to represent the process of water translation through the basin. Interpretation of the instantaneous unit hydrograph as a probability density function of translation time is demonstrated and the inverse Gaussian density proposed as a suitable functional form on physical grounds.

ISSN:0262-6667    

DOI:10.1080/02626668509490989

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626668509490990

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626668509490991

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

ISSN:0262-6667    

DOI:10.1080/02626668509490992

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor