The use of spatial information to improve hydrometric network design and evaluation

Operational needs commonly dictate the evolution of hydrometric networks. Such an approach can fail to meet strategic water management information objectives (e.g. to estimate flows at ungauged sites, to detect hydrological change). This paper examines the role of digital spatial information to inform network evolution. Capitalising on a range of catchment physical descriptors and spatial characteristics commonly used in hydrological studies, the UK National River Flow Archive (NRFA) developed two indices that assess the strategic value of individual gauged catchments, independently from the performance of the associated gauging station. The Representative Catchment Index (RCI) quantifies how representative a catchment is of a specified area, in relation to a selection of spatial characteristics. The Catchment Utility Index (CUI) examines the influence of individual catchments in the context of a regionalization method­ology used for flood estimation. A large UK catchment is used as a case study to demonstrate how these indices can support network reviews.