Links between environmental change and its impacts on river flow regime and quality in urbanising catchments

摘要

This study was undertaken to investigate the effects of urbanisation on the river flow regime andudwater quality. The links between environmental changes represented by rainfall and UrbanudExtent (URBEXT) with the changes in the river flow, river temperature and dissolved oxygenudwere explored. This thesis focuses on the following question “does urbanisation has an effect onudthe river water quantity and quality changes?”. Two urbanising catchments in the UnitedudKingdom, the river Ray at Water Eaton and the river Cut at Binfield were selected for this study.udAs a comparison, nearby similar sized rural catchments, the river Enborne at Brimpton and theudriver Winterbourne at Bagnor were also selected.udThere was no significant time-trend of rainfall found in all urban and rural catchments in alludaggregations (annual, summer and winter). For river flow, positive time-trends were found in theudtwo urban catchments in all aggregations with the exception of no significant trend was found inudthe winter in the river Cut at Binfield. The log-log regression analysis found that in the two urbanudcatchments, URBEXT alone had a strong positive relationship with the changes in mean annualudflow. When climate variability is included, the URBEXT signal was amplified. Contrasting resultsudwere found in all rural catchments where there was no significant evidence of time-trend in theudriver flow.udIncreasing temperature and dissolved oxygen values were found in all aggregations in the riverudRay, while in the river Cut these values increasing only in the winter. URBEXT had a significantudpositive relationship with temperature and dissolved oxygen in the river Ray. When rainfall andudriver flow are included, the URBEXT signal was reduced. This study also found a strong positiveudrelationship between river flow and the increase of dissolved oxygen value in the river Ray. Onudthe contrary, there was no significant time-trend in temperature and dissolved oxygen was foundudin all rural catchments.udUrbanisation was found to be a potential driver of the increase in river flow, which might lead touddetrimental rather than beneficial effects. Nevertheless, the effect on water quality wasudsomewhat spurious and showed mixed results. Despite not showing any significant trend, theudpresent temperature and dissolved oxygen values in the more natural environment of ruraludcatchments still showing a better state.