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Seasonal Flow Regimes of UK Rivers
Hannaford, J. and Buys, G. 2012. Trends in seasonal river flow regimes in the UK. Journal of Hydrology 475: 158-174.

The authors write that "the most recent outputs from the UK Climate Projections (UKCP09) initiative (Murphy et al., 2009) suggest the UK will experience wetter winters and hotter, drier summers in the future," such that there will be "decreasing [river] flows in summer, increases in winter (e.g., Arnell, 2011; Prudhomme et al., 2012), and increases in flood frequency and magnitude in some regions (Arnell, 2011; Kay and Jones, 2012; Bell et al., 2012)." But "in apparent conflict with expectations of future climate change trajectories," as derived from climate models, they report that "droughts in 2004-2006 (Marsh et al., 2007) and 2010-2012 (Marsh, 2012) have been caused by successive very dry winters, whilst a sequence of extremely wet summers occurred in the 2007-2012 period (e.g., Marsh and Hannaford, 2008)," which pair of inconsistencies between projections and reality spurred them to study the subject anew and in greater detail.

What was done
Working with daily mean river flow data obtained from the UK National River Flow Archive (Dixon, 2010), Hannaford and Buys analyzed trends in river flow between 1969 and 2008 in a network of 89 catchments from across the UK, focusing on those having "near-natural flow regimes," in order for "climate-driven trends to be distinguished from direct anthropogenic disturbances."

What was learned
In apparent harmony with climate model projections, the two researchers observed "an overall increase in winter river flows." But in conflict with what the models predict, they report that "in summer, there is no compelling evidence for a decrease in overall runoff or low flows, which is contrary to trajectories of most future projections."

What it means
First of all, in the words of Hannaford and Buys, "the predominance of increasing flow trends across the seasons, coupled with limited decreases in low flows, is favorable from a water management perspective." Secondly, "the lack of any obvious tendency towards decreasing river flows (for summer and for low flows especially) is in apparent contrast to expectations for the relatively near future under climate change scenarios." And third, "the lack of decreasing river flows may reflect some degree of resilience to anthropogenic warming."

Arnell, N.W. 2011. Uncertainty in the relationship between climate forcing and hydrological response in UK catchments. Hydrology and Earth System Sciences 15: 897-912.

Bell, V.A., Kay, A.L., Cole, S.J., Jones, R.G., Moore, R.J. and Reynard, N.S. 2012. How might climate change affect river flows across the Thames basin? An area-wide analysis using the UKCP09 Regional Climate Model ensemble. Journal of Hydrology 442-443: 89-104.

Dixon, H. 2010. Managing national hydrometric data: from data to information. In: Servat, E., Demuth, S., Dezetter, A. and Daniell, T. (Eds.), Global Change: Facing Risks and Threats to Water Resources. IAHS Press, Wallingford, United Kingdom, pp. 451-458.

Kay, A.L. and Jones, D.A. 2012. Transient changes in flood frequency and timing n Britain under potential projections of climate change. International Journal of Climatology 32: 489-502.

Marsh, T.J. 2012. UK Hydrological Bulletin: May-July 2012; and Newsletter of the British Hydrological Society, August 2012.

Marsh, T.J., Cole, G. and Wilby, R. 2007. Major droughts in England and Wales, 1800-2006. Weather 62: 87-93.

Marsh, T.J. and Hannaford, J. 2008. The 2007 Summer Floods in England and Wales - A HydrologicalAappraisal. Centre for Ecology and Hydrology, Wallingford, United Kingdom.

Murphy, J.M., Sexton, D..M.H., Jenkins, G.J., Booth, B.B.B., Brown, C.C., Clark, R.T., Collins, M., Harris, G.R., Kendon, E.J., Betts, R.A., Brown, S.J., Humphrey, K.A., McCarthy, M.P., McDonald, R.E., Stephens, A., Wallace, C., Warren, R., Wilby, R. and Wood, R.A. 2009. UK Climate Projections Science Report: Climate Change Projections. Met Office, Hadley Center, Exeter, United Kingdom.

Prudhomme, C., Young, A., Watts, G., Haxton, T., Crooks, S., Williamson, J., Davies, H., Dadson, S. and Allen, S. 2012. The drying up of Britain? A national estimate of changes in seasonal river flows from 11 Regional Climate Model simulations. Hydrological Processes 26: 1115-1118.

Reviewed 27 March 2013