Water in Celtic Countries: Quantity, Quality and Climate Variability (Proceedings of the Fourth InterCeltic Colloquium on Hydrology and Management of Water Resources, Guimarães, Portugal, July 2005).  IAHS Publ. 310, 2007, 78-85.

 

An assessment of runoff trends in undisturbed catchments in the Celtic regions of North West Europe

 

JAMIE HANNAFORD, CEDRIC L. R. LAIZE & TERRY J. MARSH

National River Flow Archive, Centre for Ecology and Hydrology, Wallingford, Oxfordshire OX10 8BB, UK

jaha@ceh.ac.uk

 

Abstract This study presents results of trend tests applied to annual and seasonal runoff time series from a network of catchments across the Celtic regions of the northwest European Atlantic margin, namely northern and western areas of the British Isles and Brittany. The aim is to provide an overview of natural, climate-driven runoff trends across the Celtic region by focusing on catchments undisturbed by artificial influences (e.g. impound­ments and hydropower development) on flow regimes. Strong evidence of increasing runoff over the 40 years from 1964 to 2003 was found for Scotland and Ireland, and there were some significant increases in Wales, western England and Brittany. The regional signals are less compelling in these areas, but the predominance of positive trends observed in this study suggests a tendency towards a region-wide increase. Annual runoff trends were associ­ated with increases in winter runoff; there was no evidence for any decline in summer runoff over the period. The findings have some parallels with climate change scenarios, although there were also strong associations with the North Atlantic Oscillation Index over the timescale used in this study. The study provides a baseline against which to assess historical variability and future runoff trends in the Celtic region.

 

Key words  climate change; monitoring networks; natural catchments; North Atlantic Oscillation; resampling; river flow; runoff; trend