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Title: East Devon public water supply strategy as assessment of the hydrological impact of the Wimbleball pump storage scheme at key sites on the River Exe
Author: R. Grew
Author: A.L. Higgins
Document Type: Monograph
SWWSL applied for a licence to abstract water from the River Exe at Exebridge for pump storage of Wimbleball Reservoir. As part of the determination of this application NRA SW undertook an assessment of the potential hydrological impact of the scheme at key sites on the River Exe between Exebridge and St. James Weir, the tidal limit. The assessment considered the impact of the scheme in relation to both the natural and existing situation. The results are presented as hydrographs and flow duration curves and are described in terms of percentage changes in flow or exceedence statistics (Q50 and Q95). Downstream of Exebridge the flows in the River Exe from January to March 1976 inclusive would be reduced by about 13% due to the abstraction. Further downstream the impact would be reduced, although downstream of Northbridge flows would be reduced by about 12% due to the increased abstraction of unsupported river water. There would, as a result of the scheme, be positive changes in the Q95 flow in comparison to the existing situation and negative changes in the Q50. The leat abstractions, particulary those at Thorverton and Pynes have the potential to create significant deprived reaches in the main river. Although the increased release of water for public water supply under the pump storage scheme would lead to increased summer flows in these deprived reaches, particularly at Oakfordbridge and Highleigh, the impact of the scheme is small relative to the potential impact of the leat abstractions. This assessment has broadly confirmed the results of SWWSL study. Differences between the statistics presented by SWWSL and the NRA generally reflect the use of different assumptions in the modelling exercise.
Publisher: National Rivers Authority
Publication Date: 1993
Publication Place: Exeter
Subject Keywords: Water abstractionRiver levelFlow rateWater industryHydrographyRivers
Geographic Keywords: ExeEast Devon catchmentDevon
Extent: 20; + figures, tables and appendices
Total file downloads: 291

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