Do catchment characteristics explain differences in coherence and trends in hydroclimatic behaviour in an upland region?

To explore the link between catchment characteristics and sensitivity to environmental change, longer-term data from 21 contrasting mesoscale (67–690 km2) catchments in northern Scotland were analysed to examine the influence of hydroclimatic drivers on hydrological response. Cluster analysis was used to classify the catchments into four distinct groups, with topography and annual precipitation being the two most significant differentiating factors. Using 12 years of data from the 21 sites, inter-catchment coherence of intra- and inter-annual variation of precipitation, air temperatures and stream discharge were assessed both within and between clusters. Whilst catchments in clusters characterised by lower elevations exhibited coherence in hydroclimatic drivers and streamflow response, the higher altitude catchments did not. Annual trends were evident for widespread increases in temperature and also increasing values of precipitation in the higher elevation catchments. Seasonal trends indicate a lack of consistent change during winter, but most other seasons exhibit an increase in temperatures, with isolated increases in measures of precipitation and discharge particularly during the transitional seasons of spring and autumn. These trends ultimately could not be related with catchment typology where increasing upland area results in a breakdown of hydroclimatic coherence between sites.