No description available.

Rutland Water is a large (1260 ha) eutrophic pumped- storage reservoir in the lowland east midlands of England, impounded in 1975. Artificial mixing during the summer is continuous but weak, with a polymictic regime controlled by wind mixing. The crustacean zooplankton was studied during 1984 and 1985. Daphnia hyalina forma lacustrls Sars was the dominant limnetic cladoceran, with Daphnia pulex (De Geer), Bosmlna longlrostrls (O.F. Muller) and Leptodora klndtl (Focke) also present. Six limnetic copepods were present: Eudlaptomus gracilis (Sars), Eurytemora velox (Li 11jeborg), Cyclops abyssorum Sars, Cyclops vlclnus Uljanin, Acanthocyclops robustus (Sars) and Mesocyclops leuckartl (Claus). Cyclops vlclnus entered diapause as copepodite IV in May, emerging during November-March.' Reproduction was more synchronous than expected from the period of emergence and could not be explained in terms of temperature-dependent development times alone. Food availability may have limited reproduction until the spring diatom peak. The mean species richness of copepods, at 5*2, was unusually high. Species composition had changed since impoundment and this richness might represent a transition from founder species to successful immigrants. Possible mechanisms of coexistence for the calanoid species and for Cyclops species were discussed: exclusion may not occur. Features which distinguish copepodite larval instars are well known. Determination of the calanoid species was possible in all instars but the cyclopoid species were less distinct. Cyclopoids in the fifth copepodite stage showed many adult characters but earlier instars of different species did not differ qualitatively with respect to the features which were examined. The vertical distribution of Crustacea was similar to that typical of stratifying lakes, with highest densities of all groups in the upper part of the column. Agreement was found with the buoyancy/current model of large-scale horizontal patchiness. It was suggested that the effects on horizontal patchiness of *'conveyor-belt" currents should be greater in the mixed column due to a more complete coincidence of zooplankton abundance maxima and the leeward wind-driven flow.

In the course of my duties as a hydrologist with a British regional water authority, I am frequently required to derive riverflow statistics for catchments for which there is little or no measured flow data. Whilst there are many existing methods by which flows may be estimated, my experience has been that the majority of these approaches are unreliable. This thesis describes the development of a suite of alternative, user orientated, high and low flow estimation techniques for application in ungauged catchments. As the derived methods require the cross reference between a large number of figures, these have grouped together as a separate volume, together with appendicies which include all analysed data. However, second copies of selected figures and all summary tables have been included within the main text as an aid to explanation.

No description available.

No description available.

The aim of this research is to determine the process by which runoff draining parts of the UK uplands becomes discoloured. Recent increases in colour are perceived as a problem due to the frequency with which EC surface water directives are breached, to the increased cost of meeting standards, to an increase in consumer complaints, and due to the possible deleterious health effects of consuming coloured potable water. The work was conducted over the last four years, largely in the Upper Burn and Nidd valleys, north Yorkshire, and at the University of Leeds. Existing knowledge on the chemical nature and environmental genesis of coloured water is reviewed, and related to the chemical nature of coloured waters examined in this study. Analysis of water quality archives and direct monitoring of selected catchments was conducted enabling the spatial and temporal distribution of coloured waters to be determined. A tentative process theory was produced, and tested by controlled laboratory investigations. Coloured runoff is derived from Winter Hill soil, raw acid oligo-fibrous peat, and is most intense from areas with slopes < 5% and high drainage densities. The seasonal pattern of colour is highly regular, and is a product of rainfall and soil moisture deficit. Colour is strongly associated with discharge, and demonstrates the operation of a catchment flushing mechanism. Runoff is discoloured in a three phase process; colour production, solubilisation and removal. Colour is a product of organic decomposition, dependent upon microbiological activity, moisture deficit, temperature and peat structure. Solubilisation of colour is dependent upon solution pH, temperature, the chemical structure of organic molecules and the availability of iron. The removal of decomposition products, as colour, is strongly dependent on the moisture status of peat, and its ability to rewet after drying. The implications of these findings for future colour levels and for catchment and catchwater management are discussed.

No description available.

The downstream influence of storage reservoirs upon river water chemistry is an area largely devoid of literature. Yet approximately fifty per cent of such reservoirs in Great Britain significantly regulate flow, both by flood control, and increasingly through irregular but discrete large-volume releases. Natural patterns of stream water chemistry are shown to be disturbed by the effects of Man, through changing land-use and effluent discharge. Moreover, the establishment of a reservoir in the head waters of a major river, can change the water quality regime for a considerable distance below the dam.

No description available.

The regulation of the Manama river, one of the major Orinoco distributary channels, has instigated changes in the hydrological and sedimentological regimes of its channel and surrounding wetlands, covering one-third of the Delta area. The dam has altered the hydrodynamics of the Manama. While the average flow of its channel was reduced from 10% to 0.5% (200 m3/s), of the annual discharge of the Orinoco River. The adjacent Macareo distributary, which is not regulated, discharges 11% (4,000 m3/s) annually. During the seasonal high-water period, the water level in the Macareo rises approximately 7 m, while in the Manama is restricted to an periodic oscillation of 0.7 to 1.2 m due mainly to the tidal influence. This flow reduction not only affects the accretion and erosive processes of the banks, due to the decrease of transport of sediments, but also the composition, distribution and diversity of aquatic plants in the region, particularly along the river shores where the species diversity tend to be lower in the regulated river than in the unregulated. The change in the hydrologic dynamic has promoted broad floating meadows to develop in the upper reaches of the Manama river creating patches of rafting meadows. The cessation of the annual flooding has allowed an extensive intrusion of saline water from the sea, which only occur during the dry season. This has enabled halophytic species, particularly mangrove communities to expand their distribution upriver and has also forced the migration of part of the Delta inhabitants Creole and Indians, resulting in a modification of the distribution of the forest and marsh ecological communities due to the overexploitation of their subsistence resources. The particular characteristics of the region that have remained mostly undisturbed since the dam construction several decades ago, permit a comparison of 30 years period of the long-term physical and biological characteristics of a regulated (Manamo) and unaltered (Maca reo) distributary. This thesis investigates these changes and propose a model of the river regulation effects on the ecosystem properties and an equilibrium model of the disturbance and the gain of a new steady state of the ecosystems compartments.