Changing flow regime of a Cairngorm river: identifying emerging patterns and potential drivers from long-term data

Abstract

Climate change will alter patterns of landscape water movement and resulting streamflow generation processes, as precipitation and evapotranspiration dynamics change. Given their altitude and latitude, Scottish Cairngorm rivers are amongst Europe’s most sensitive to such alterations due to reduced snowfall and changing snowmelt dynamics. We contextualise recent changes in streamflow dynamics to longer-term variations using a near-100-year discharge timeseries from the Aberdeenshire River Dee. Similar long-term records of precipitation and air temperature, plus recent satellite-derived snowpack data, were available to assess correspondence between hydroclimatic drivers and discharge. The last decade was characterised by notable extremes; 2015's Storm Frank bringing the largest flood since 1829, followed by the most severe drought since the 1970s (2016–2018). Recent summer low flows have tended to start earlier and persist longer. Variations in other metrics (e.g. median flows) remained similar. Locally Estimated Scatter Plot Smoothing showed patterns of streamflow variation generally followed trends in precipitation. Precipitation∼streamflow correlations increased post-1975, likely reflecting reducing snowpacks. Impacts include increased flooding, reduced water availability and changing aquatic habitats, though ostensibly intuitive mitigation such as tree planting for flood reduction may be ineffective. Management responses to mitigate the effects of climate change on streamflows need to be considered and evidence-based.