Articles | Volume 14, issue 12
Hydrol. Earth Syst. Sci., 14, 2367–2382, 2010
Hydrol. Earth Syst. Sci., 14, 2367–2382, 2010

Research article 01 Dec 2010

Research article | 01 Dec 2010

Streamflow trends in Europe: evidence from a dataset of near-natural catchments

K. Stahl1,2, H. Hisdal3, J. Hannaford4, L. M. Tallaksen1, H. A. J. van Lanen5, E. Sauquet6, S. Demuth7, M. Fendekova8, and J. Jódar9 K. Stahl et al.
  • 1Department of Geosciences, University of Oslo, Oslo, Norway
  • 2Institute of Hydrology, University of Freiburg, Freiburg, Germany
  • 3Norwegian Water Resources and Energy Directorate, Oslo, Norway
  • 4Centre for Ecology and Hydrology, Wallingford, UK
  • 5Hydrology and Quantitative Water Management Group, Centre for Water and Climate, Wageningen University, Wageningen, The Netherlands
  • 6UR Hydrologie-Hydraulique Cemagref, Lyon, France
  • 7Division of Water Sciences, Section of Hydrological Processes and Climate, Natural Sciences Sector, UNESCO, Paris, France
  • 8Department of Hydrogeology, Faculty of Natural Sciences, Comenius University in Bratislava, Bratislava, Slovakia
  • 9Institute of Environmental Assessment and Water Research (IDAEA-CSIC), Barcelona, Spain

Abstract. Streamflow observations from near-natural catchments are of paramount importance for detection and attribution studies, evaluation of large-scale model simulations, and assessment of water management, adaptation and policy options. This study investigates streamflow trends in a newly-assembled, consolidated dataset of near-natural streamflow records from 441 small catchments in 15 countries across Europe. The period 1962–2004 provided the best spatial coverage, but analyses were also carried out for longer time periods (with fewer stations), starting in 1932, 1942 and 1952. Trends were calculated by the slopes of the Kendall-Theil robust line for standardized annual and monthly streamflow, as well as for summer low flow magnitude and timing. A regionally coherent picture of annual streamflow trends emerged, with negative trends in southern and eastern regions, and generally positive trends elsewhere. Trends in monthly streamflow for 1962–2004 elucidated potential causes for these changes, as well as for changes in hydrological regimes across Europe. Positive trends were found in the winter months in most catchments. A marked shift towards negative trends was observed in April, gradually spreading across Europe to reach a maximum extent in August. Low flows have decreased in most regions where the lowest mean monthly flow occurs in summer, but vary for catchments which have flow minima in winter and secondary low flows in summer. The study largely confirms findings from national and regional scale trend analyses, but clearly adds to these by confirming that these tendencies are part of coherent patterns of change, which cover a much larger region. The broad, continental-scale patterns of change are mostly congruent with the hydrological responses expected from future climatic changes, as projected by climate models. The patterns observed could hence provide a valuable benchmark for a number of different studies and model simulations.