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This thesis aims to fiimish an understanding of the water fluxes and storages occurring at the subcatchment scale in Goss Moor, a large lowland wetland in Cornwall, UK. Goss Moor constitutes approximately 5 km^ of poor fen and similar wetland areas sited on clayey alluvial and periglacial deposits in the base of a broad/shallow headwater valley. The bedrock is kaolinised granite and pelite. The hydrological characterisation was achieved using variables measured directly on site, using spectrally derived stream flow components and using flows output from a caUbrated numerical model of transient groundwater flow beneath the wetland. The study demonstrated the use of distributed spectral filtering for source area characterisation and of numerical modelling for investigathig the role of groundwater flow in the wetland. Certain stream flows into and out of the wetland were monitored at an hourly resolution. At each site, slowly- and quickly-varying components of flow were discriminated using a digital filter whose response was based upon an observed summer recession. Quick flows thus defined were found to be conserved during translation from the upsfream inputs to the outflow, although in-channel dispersion eliminated their flashiness. Conversely, the slow flow component was found to vary more rapidly at the wetland outflow than at the main stream entry, indicating the dominance of a different source of flow upon exit from the wetland. Overall stream flow gained by 50% in traversing the wetland site. Evapotranspiration (ET) rates in the wefland and in the outer catchment were estimated using the Penman-Monteith formula with measurements near or within the site. The calculations indicated that evapotranspirative losses would be greater from the wefland than from the remainder of its catchment due to the presence of surface water. U.S.G.S. MODFLOW was used to model the groundwater flow in the alluvium beneath the wefland. Shallow groundwater levels at 20 piezometer sites within the wefland, together with information on stratigraphy, rainfall and ET, provided boundary and caUbration data for the model. The results of in situ slug tests were used to define the aquifer permeability for the model in the transient calibration. Storativity and ET were adjusted to produce a match with the observed summer water table decline. A reduction of ET with falling water table greatly improved the match, and it was postulated that the declining water table had therefore dropped below the zone of greatest evapotranspirative uptake. By combining the various sources of data, the wefland's water budget was estimated. The numerical modeUing showed that groundwater flow to the river accounted for between only 0% and 3% of the total output from the wefland surface and substrata. ET accounted for 20% and surface runoff for 77-80%. Although wefland surface flow was not measured, the water budget showed that a substantial summer reduction in stored water would result if no peripheral inflows were received onto the wetiand surface. In the annual water budget, such peripheral inflows were of a magnitude similar to that of the rainfall input to the wefland. Together, these two inputs traversed the wefland surface to provide the increase in slow flow in the river on its exit from the wetiand. The implications of the water budget for the management of the wetland are briefly discussed.

The development and field testing of a particle tracing technique for the prediction and monitoring of cohesive sediment transport is described. Natural, chemical and water soluble dye tracers have been used for many years to determine water circulation in order to predict sediment transport. Radioactive and fluorescent particles have been used widely to predict sediment particle transport, but have been restricted mainly to non-cohesive sand and gravel transport studies due to the difficulties of preparation, handling, disassociation of the label from the particle and labour-intensive analysis. The development of a fine cohesive tracing technique therefore offered a significant advancement for the understanding and prediction of fine cohesive sediment and pollutant dynamics in aquatic environments if a sediment analogue could be developed. The physical properties, including size, surface charge, fiuorescence and settling velocity of natural fine cohesive sediment were analysed in order to passively and actively adsorb organic fluorescent dyes onto the sediment surface; the tests were largely unsuccessful. The physical properties of artificial fluorescent particles as sediment analogues were examined and found to have a close correlation to natural sediment. Analysis of the fluorescent particles in mud suspensions on an Analytical Flow Cytometer offered an automated and accurate method of tracer concentration determination at low dilutions. A preliminary field study was carried out in a small pool with encouraging results. A study in a shallow freshwater lake was carried out to determine the sediment dynamics in the lake. A depth-averaged model of the wind-driven circulation within the lake was used to interpret the distribution of tracer. Secondary transport and deposition clearly led to an accumulation of sediment and internal loading in the lake driven by hydrodynamical forcing. A study of the particle residence time and deposition-resuspension processes in the turbidity maximum of a macro-tidal estuary. Fluorescent particles were released into the turbidity maximum and were advected down-estuary on the ebb tide and up-esiuary on the flood tide. The residual mass budgets indicated a significant deposition of the particles in the upper estuary at slack high water. The particles were detected in estuarine surface waters 1 week after release. The fluorescent particles behaved in a similar way to the suspended sediment in both the lacustrine and estuarine study and were considered as sutiable tracers for cohesive sediment.

No description available.

No description available.

No description available.

Current applications of the critical loads concept are geared primarily towards targeting emission control strategies at a national and international level. In the UK maps of critical loads for freshwaters are available at 10km2 resolution based on a single representative site in each grid square. These maps do not take variations of water chemistry within mapping units into account and are therefore of limited use for application to non-mapped sites. This thesis describes the development of an empirical statistical model, which uses nationally available secondary data, to predict freshwater critical loads for catchments lacking the appropriate water chemistry information. A calibration exercise using data from 78 catchments throughout Scotland is described. Water chemistry for each catchment has been determined and each catchment is characterised according to a number of attributes. Multivariate statistical analysis of these data shows clear relationships between catchment attributes and water chemistry and between water chemistry and diatom critical load. The key variables which explain most of the variation in critical load relate to soil, geology and land use within the catchment. Using these variables (as predictors) in a regression analysis diatom critical load could be predicted across a broad gradient of sensitivity (R2adj = c. 0.8). The predictive power of the model was maintained when different combinations of explanatory variables were used. This accords the model a degree of flexibility in that model paramaterisation can be geared towards availability of secondary data. There are limitations with the model. These relate to the nature of the predictor variables and the ability of the model to predict critical loads for more sensitive sites. Nevertheless the ability of the model to differentiate between sensitive and non-sensitive sites offers considerable scope for environmental managers to undertake national inventories of catchment sensitivity and specific assessments of individual catchments.

No description available.

No description available.

No description available.