A primary function of the National River Flow Archive project at the Centre for Ecology & Hydrology is to maintain a overview of network evolution and identify sub-networks of particular strategic importance – for example to help monitor drought extent and severity, identify hydrological trends, help in the development of tools to improve engineering design procedures or river and water management (e.g. to allow the assessment of the frequency of extreme flows at ungauged sites) or allow a deeper scientific understanding of hydrological processes.
As in any monitoring programme, data from individual gauging stations contribute unevenly to the overall information output from the UK network. Whilst many gauging stations are necessarily sited to satisfy clear operational needs (e.g. monitoring flows upstream of a major abstraction), others with a much less evident operational role may have considerable strategic value. Many small catchments fall into this category particularly if the hydrometric performance of the gauging station is good and the flow regime is sensibly natural. Such stations contribute disproportionately to the advancement of hydrological science and, crucially, quantifying the impact of climate variability and change on river flow patterns to be effectively indexed.
Identification of those catchments, and gauging station with the greatest strategic utility helps to inform decisions on future network rationalisation exercises and provides a framework within which bespoke networks can be designated to address particular information demands – for example assessing runoff at the national scale or identifying long term trends in river flows (see NRFA Categories and Networks).