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Title: Semi-natural vegetation characteristics and the prediction of hydrological and hydrochemical information within moorland, acid-sensitive catchments in upland Wales
Author: Renshaw, K. J.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1994
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This study investigates the potential of utilizing semi-natural vegetation characteristics to predict hydrological and hydrochemical source areas in upland moorland catchments. It centres upon the intensive vegetational, hydrological and hydrochemical investigation of the Nant Gruffydd catchment, a tributary of the Camddwr at Llyn Brianne in upland, mid-Wales. A nested catchment approach was adopted and intensive monitoring during baseflows and stormflows was used to establish hydrological and hydrochemical source areas at stages through the storm hydrograph. The hydrological points raised include: 1) plateau peatlands ranked as the most important hydrological source during typical storm events, whilst the lower valley riparian peat areas ranked most important during very large storms and/or under very wet antecedent conditions. 2) isotopic investigations, although suggesting that 'old' pre-event water are dominant in the stream hydrograph in typical storm events, also demonstrate the invalidity of assumptions involved in conventional isotopic separation techniques. 3) hypotheses linking rapid runoff mechanisms with the delivery of pre-storm waters can be envisaged and are proposed. The hydrochemical points raised include: 1) the Nant Gruffydd catchment exhibits spatially variable levels of acidity and aluminium, specifically, plateau peatlands are characterised with low pH levels (4.2-4.4 pH units) and ranked as the most important source of Hydrogen, and the catchment slopes with mineral soils were identified as important sources of Aluminium (7 mmols/l) and supplied water of higher pH helping to account for the pH of 5.5 at the catchment outlet. 2) aluminium levels in the mid to upper catchment were as high as those recorded in acidified afforested catchments in the UK (Hornung et al. 1987). 3) changes in within-catchment sources of runoff, as opposed to at-a-point chemical changes exert a prime influence upon the hydrochemical dynamics of streamwater. 4) within-channel chemical reactions appear to influence runoff hydrochemistry more than hitherto has been recognised. The data gathered enabled associations between vegetation patterns and different hydrological/hydrochemical parameters to be explored at three scales. Whilst this demonstrated potentially useful associations, multiple-regression analysis failed to establish strong relationships.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available