Fine substrate sediments are considered to be important in the management of urban river systems. Urban construction activities have been reported to increase sediment loads causing the temporary siltation of channel substrates within the urban area. Nevertheless fine sediment derived from urban areas frequently carry toxic material well in excess of background concentration levels. While the soluble phase of heavy metals and the importance of their association with suspended sediment has received considerable attention, longer term studies of fine urban river-bed sediments are limited. Furthermore studies of heavy pollutants in active stream sediments, below mine waste tips, have shown the channel substrate can provide a long term store for heavy metals in association with fine sediments. This thesis investigates the variety of impacts that urbanisation has upon the sedimentation of gravel bed rivers. A freeze coring technique and infIltration baskets have been used to study the textural-geochemical properties of fme matrix sediment and its development within an urban river-bed framework, within and below a number of contrasting urban catchments in the U.K. Complex urban hydrological and sedimentological regimes are shown to have a variable influence upon matrix sedimentation. The actual volume of matrix present within the urbanised substrate is influenced by the degree of urbanisation within the catchment. Furthermore this sediment is finer in size and associated heavy metal concentrations are well in excess of natural background levels. Although heavy metal levels do correlate slightly with textural characteristics, the presence of maximum concentrations at depth in the substrate indicate possible mobilisation of metals within the urbanised river-bed. The temporal behaviour of matrix development within an urbanised substrate is shown to differ from natural river-beds. Despite high suspended sediment concentrations the magnitude of the potential rate of supply is lower, by 50 percent, and dominated by organic material. This sediment also contains elevated heavy metal cocnentrations. This contrasts to the inorganic sediment ingress of natural river substrates. It is concluded that fine matrix sediments within urban gravel bed rivers should be at least of concern to public health engineers, water authorities and conservationists.

No description available.

There are many circumstances where lateral flows in the upper soil layers above the regional groundwater table are important for hillslope and catchment hydrology, and in particular for the transport of contaminants. Perched water tables frequently occur in Quaternary drift sequences, reducing rates of recharge to the underlying aquifers and altering contaminant migration pathways; recent experimental and modelling studies have demonstrated the potential importance of lateral flows in the unsaturated zone, even in homogeneous soils; and lateral interflow at the hillslope scale, and its role in generating storm runoff, is the subject of intense current debate amongst hydrologists. A numerical model for simulating transient three-dimensional variably-saturated flow in complex aquifer systems (the Variably-Saturated Subsurface flow, or VSS, model), capable of representing these conditions, is presented in this thesis. The VSS model is based on the extended Richards equation for saturated as well as unsaturated conditions, and also includes capabilities for modelling surface-subsurface interactions, stream-aquifer interactions, prescribed head and flow boundary conditions, plant and well abstractions, and spring discharges. A simple but novel approach is taken to solving the three-dimensional non-linear Richards equation on a flexible-geometry finite-difference mesh, using Newton-Raphson iteration and an adaptive convergence algorithm. The VSS model is implemented as a module of the catchment flow and transport modelling system, SHETRAN. The reliability of the full SHETRAN modelling system is demonstrated using verification and validation tests, including comparisons against analytical solutions for simple cases, and simulations of storm runoff in a small Mediterranean catchment. Simulations of flow and contaminant transport in complex sequences of Quaternary drift deposits demonstrate the full capabilities of the modelling system under real-world conditions.

An inability to calculate the balance between supply and demand may mean an inability to meet standards of service or, arguably worse, an excessive provision of water resources and excessive costs to customers. United Kingdom Water Industry Research Limited (UKWIR) Headroom project in 1998 provided a simple methodology for the calculation of planning margins. This methodology, although well received, was not, however, accepted by the Regulators as a tool sufficient to promote resource development. This thesis begins with considering the history of water resource planning in the UK, moving on to discuss events following privatisation of the water industry post-1985. The mid section of the research forms the bulk of original work and provides a scoping exercise which reveals a catalogue of uncertainties prevalent within the supply-demand balance. Each of these uncertainties is considered in terms of materiality, scope, and whether it can be quantified within a risk analysis package. Many of the areas of uncertainty identified would merit further research. A workable, yet robust, methodology for evaluating the balance between water resources and water demands by using a spreadsheet based risk analysis package is presented. The technique involves statistical sampling and simulation such that samples are taken from input distributions on both the supply and demand side of the equation and the imbalance between supply and demand is calculated in the form of an output distribution. The percentiles of the output distribution represent different standards of service to the customer. The model allows dependencies between distributions to be considered, for improved uncertainties to be assessed and for the impact of uncertain solutions to any imbalance to be calculated directly. The method is considered a significant leap forward in the field of water resource planning.

In recent years there has been a great effort to combine the technologies and techniques of GIS and process models. This project examines the issues of linking a standard current generation 2½d GIS with several existing model codes. The focus for the project has been the Shropshire Groundwater Scheme, which is being developed to augment flow in the River Severn during drought periods by pumping water from the Shropshire Aquifer. Previous authors have demonstrated that under certain circumstances pumping could reduce the soil moisture available for crops. This project follows earlier work at Aston in which the effects of drawdown were delineated and quantified through the development of a software package that implemented a technique which brought together the significant spatially varying parameters. This technique is repeated here, but using a standard GIS called GRASS. The GIS proved adequate for the task and the added functionality provided by the general purpose GIS - the data capture, manipulation and visualisation facilities - were of great benefit. The bulk of the project is concerned with examining the issues of the linkage of GIS and environmental process models. To this end a groundwater model (Modflow) and a soil moisture model (SWMS2D) were linked to the GIS and a crop model was implemented within the GIS. A loose-linked approach was adopted and secondary and surrogate data were used wherever possible. The implications of which relate to; justification of a loose-linked versus a closely integrated approach; how, technically, to achieve the linkage; how to reconcile the different data models used by the GIS and the process models; control of the movement of data between models of environmental subsystems, to model the total system; the advantages and disadvantages of using a current generation GIS as a medium for linking environmental process models; generation of input data, including the use of geostatistic, stochastic simulation, remote sensing, regression equations and mapped data; issues of accuracy, uncertainty and simply providing adequate data for the complex models; how such a modelling system fits into an organisational framework.

No description available.

This project examined the trace-element and stable-isotope composition of non-marine ostracod shells and their use in Holocene palaeoclimate reconstruction, with particular reference to mid-latitude shallow carbonate lakes. Controls on the chemical composition of shells from such environments were studied. Results were used to test the application of ostracod shell chemistry data to palaeoclimate reconstruction. Selected techniques were applied to a high resolution study of Holocene lake marl sequence. The project investigated influences on shell chemistry during formation, sedimentary deposition and extraction. A core covering approximately 9,450 to 5,800 Cal. Yr BP was taken from Cunswick Tarn, Cumbria, yielding ostracod faunal and shell chemistry data used to produce a palaeoclimate interpretation for the early Holocene. This interpretation agreed with studies showing a warm, dry early Holocene and a cooler, wetter mid-Holocene. Seasonal sampling of water and ostracods at Cunswick Tarn provided a modern analogue for the core material. Species-specific fractionations of stable isotopes were similar to findings from ponds in Greywell, Hampshire. There were seasonal variations in the trace-element composition of shells, which may reflect: seasonal fluctuations; shell growth following initial calcification; and cleaning problems. Monthly sampling of water and ostracods was performed at carbonate ponds near Greywell. Species-specific fractionations of oxygen isotopes were observed. Compared to theoretical equilibrium calcite, all species exhibit [delta][sup]18 O values more positive than expected, while [delta][sup]13 C values equal equilibrium values. Variations in shell trace-element composition was greater than that of the water. This result may be related to animal physiology and the water’s low trace-element content. Ostracods collected from additional sites with elevated Mg/Ca[sub](water) ratios showed the best correlation between the Sr/Ca ratio of the water and the Sr/Ca of the shell. Effects of established cleaning techniques on shell chemistry were investigated. Whenever possible, only brush cleaning with deionised water should be used. Sodium hypochlorite is recommended for any further cleaning. An investigation of the effect of partial dissolution on shell chemistry demonstrated that even extremely degraded Cypretta brevisaepta shells have similar trace-element and stable-isotope ratios to unaltered shalls. However, dissolution may alter shell chemistry, and whenever possible, pristine shells should be used. Pseudocandona rostrata specimens from Greywell were grown in vitro. Adults had low weight with low M/Ca ratios. The Sr/Ca[sub](ostracod) ratios were negatively correlated with weight, while M/Ca[sub](ostracod) ratios were weakly positively correlated with M/Ca[sub](water), Sr/Ca[sub](water), and temperature. The research shows that a knowledge of the life-history and ecology of ostracods, together with the chemical signals recorded in their shells, can provide an effective tool for the interpretation of palaeoclimatic events.

The ground water regimes of three small, undisturbed (natural) and accessible hard rock catchments representing the South, Midlands and the North of Great Britain have been hydrogeologically investigated and compared. There is a dearth of hydro geological information on hard rock areas in Britain. This is because the general availability of surface water and extensive sedimentary aquifers has not encouraged ground water prospecting in hard rock areas. In view of this, low flow study was considered essential since geology exerts a great influence on its characteristics. This was carried out using baseflow recession analysis. From a combination of practical, empirical and theoretical considerations aided by statistical analysis on a computer, baseflow recession constants which dynamically reflect the physiographic and geologic controls within a catchment were derived for the catchments investigated. These were used to characterise the behaviour of the low flows. A new method which is free of random selection of data for baseflow recession analysis is presented and a model for the curve fitting both by computer and manual methods are fully discussed and its application is also presented. Water balance computations for each of the three catchments is presented in chapter 2. Lithological units were identified by a detailed geological study. These were further investigated using resistivity and electromagnetic methods of geophysical survey. Hydrogeological properties of the aquifers were investigated by pumping test analysis and subsequent comparison of hydraulic conductivities from soils and baseflow studies. A water chemistry investigation of spring, river and rain waters has been carried out to try and defme flow paths of the ground water and this is presented in chapter 7. From these investigations, this research concludes that large community water supplies through boreholes can be economical only in one of the catchments (East Dart catchment). In the other two catchments (Blackbrook and Calder catchments), small community and household supplies are possible through boreholes (in some areas) and large diameter wells.

The techniques for computing dam-break flood waves in prismatic channels are reviewed. Numerical models for cases with or without an initially dry downstream bed are developed. The models are based on the characteristic forms of the shallow water equations, both in (X-T) and (R-T) space, using specified time intervals and incorporating the Rankine-Hugoniot shock equations. Three numerical models for rectangular section channels are studied, namely the parallel (X-T), the expanded (R-T) and the contracted (R-T) cases; any two of these are then linked to produce three further models, described as the Contracted-Plain (RT-XT), the Contracted-Expanded (RT-RT) and the Plain-Expanded (XT-RT) models. Four physical models were tested and compared with results from the numerical models and with those from Barr and Das (1980), Marshall and Menendez (1981) and Katopodes and Schamber (1983). The numerical and experimental results are given in the form of comparative plots of front heights, surface profiles, front trajectories and depth hydrographs. Variations from the well-known solutions by Ritter (1892) and Stoker (1957), including those caused by radial flow effects are found to occur and are discussed.

No description available.