Climate and Rivers

Over the last few decades as hydrologists have slowly raised their line of sight above the watershed boundary, it has become increasingly recognised that what happens in the atmosphere, as a major source of moisture for the terrestrial branch of the hydrological cycle, can strongly influence river dynamics at a range of spatial and temporal scales. Notwithstanding this, there is still a tendency for some in the river research community to restrict their gaze to the river channel or floodplain. However Geoff Petts, the person to which this special issue is dedicated, understood well and widely encouraged a holistic view of river catchment processes. This included an acknowledgment of the role of climate, in its broadest sense, in shaping what happens within and without the river channel. The purpose of this paper therefore is to offer a broad overview of the role of some aspects of climate science in advancing knowledge in river research. Topics to be addressed include the role of climate in influencing river flow regimes, a consideration of the large scale climate mechanisms that drive hydrological variability within river basins at inter-annual to decadal timescales and atmospheric rivers and their link to surface hydrology. In reviewing these topics a number of key knowledge gaps have emerged including attributing the causes of river flow regime changes to any one particular cause, the non-stationary and asymmetric forcing of river regimes by modes of climate variability and establishing links between atmospheric rivers, and terrestrial river channel processes, fluvial habitats, and ecological change