A consideration of rainfall, runoff and losses at Plynlimon in the context of long term hydrological variability in the UK and maritime Western Europe S. Green and T. J. Marsh Institute of Hydrology, Wallingford, UK
Abstract. Important questions concerning the resilience of current
water management strategies have been raised by the recent volatility of
climatic conditions across large parts of western Europe. The last decade,
overall, has been exceptionally warm and there have been very large spatial
and temporal variations in rainfall, river flows and aquifer recharge rates.
Examination of historical rainfall and runoff records for parts of maritime
western Europe confirms that there is no close modern parallel to the conditions
experienced recently. Some-but far from complete-consistency with a number
of favoured climate change scenarios may be recognised.
Analyses of recent trends in lengthy rainfall and
runoff series for the UK demonstrate significant regional differences and
provide conflicting signals especially in relation to trends in catchment
losses. Difficulties in reconciling the results from different areas may
reflect both real hydroclimatological differences between catchments and
variations in the precision of hydrometric time series-uncertainties in
the assessment of areal precipitation in upland areas in particular. The
dense monitoring networks at Plynlimon together with a rigorous data quality
control programme underpins the value of the hydrometric datasets as important
benchmarks against which to assess the significance of the very unusual
patterns of rainfall and runoff which have characterised the recent past.
This paper places the rainfall, runoff and losses
data for Plynlimon in the perspective provided by a number of long hydrometric
records for maritime western Europe. The representativeness of the Plynlimon
base period is considered with particular reference to both the historical
stability which typifies the great majority of European hydrometric time
series and the recent extension in the recorded range of accumulated rainfall
and runoff totals which has been identified in some regions (e.g. western
Scotland and Norway). Particular attention is directed to changes in seasonal
rainfall and runoff patterns and the recent increases in evaporative demands.
Some of the implications for the overall water balance and for water resource
management are considered.
Citation: Green, S. and Marsh, T. J.: A consideration of rainfall, runoff and losses at Plynlimon in the context of long term hydrological variability in the UK and maritime Western Europe, Hydrol. Earth Syst. Sci., 1, 399-407, doi:10.5194/hess-1-399-1997, 1997.