Document Detail

Hydrology and water quality of the headwaters of the River Severn: Stream acidity recovery and interactions with plantation forestry under an improving pollution climate.
MedLine Citation:
PMID:  20708776     Owner:  NLM     Status:  MEDLINE    
This paper presents new information on the hydrology and water quality of the eroding peatland headwaters of the River Severn in mid-Wales and links it to the impact of plantation conifer forestry further down the catchment. The Upper Hafren is dominated by low-growing peatland vegetation, with an average annual precipitation of around 2650 mm with around 250 mm evaporation. With low catchment permeability, stream response to rainfall is "flashy" with the rising limb to peak stormflow typically under an hour. The water quality is characteristically "dilute"; stormflow is acidic and enriched in aluminium and iron from the acid organic soil inputs. Baseflow is circum-neutral and calcium and bicarbonate bearing due to the inputs of groundwater enriched from weathering of the underlying rocks. Annual cycling is observed for the nutrients reflecting uptake and decomposition processes linked to the vegetation and for arsenic implying seasonal water-logging within the peat soils and underlying glacial drift. Over the decadal scale, sulphate and nitrate concentrations have declined while Gran alkalinity, dissolved organic carbon and iron have increased, indicating a reduction in stream acidification. Within the forested areas the water quality is slightly more concentrated and acidic, transgressing the boundary for acid neutralisation capacity as a threshold for biological damage. Annual sulphate and aluminium concentrations are double those observed in the Upper Hafren, reflecting the influence of forestry and the greater ability of trees to scavenge pollutant inputs from gaseous and mist/cloud-water sources compared to short vegetation. Acidification is decreasing more rapidly in the forest compared to the eroding peatland possibly due to the progressive harvesting of the mature forest reducing the scavenging of acidifying inputs. For the Lower Hafren, long-term average annual precipitation is slightly lower, with lower average altitude, at around 2520mm and evaporation is around double that of the Upper Hafren.
Colin Neal; Mark Robinson; Brian Reynolds; Margaret Neal; Philip Rowland; Simon Grant; David Norris; Bronwen Williams; Darren Sleep; Alan Lawlor
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2010-08-13
Journal Detail:
Title:  The Science of the total environment     Volume:  408     ISSN:  1879-1026     ISO Abbreviation:  Sci. Total Environ.     Publication Date:  2010 Oct 
Date Detail:
Created Date:  2010-08-30     Completed Date:  2010-10-29     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0330500     Medline TA:  Sci Total Environ     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  5035-51     Citation Subset:  IM    
Copyright Information:
Copyright 2010 Elsevier B.V. All rights reserved.
Centre for Ecology and Hydrology, Wallingford, Crowmarsh Gifford, Wallingford, OXON, OX10 8BB, UK.
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MeSH Terms
Acids / analysis*
Aluminum / analysis
Environmental Monitoring*
Hydrogen-Ion Concentration
Rivers / chemistry*
Water Pollutants, Chemical / analysis*
Water Pollution / prevention & control,  statistics & numerical data
Reg. No./Substance:
0/Acids; 0/Water Pollutants, Chemical; 7429-90-5/Aluminum

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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