Derivation of the UK national and regional runoff series

This technical report details the derivation and updating of the daily and monthly outflow series for the UK and its constituent parts. These series are widely exploited in the National Hydrological Monitoring Programme (NHMP), to meet international data exchange obligations, and in an extensive range of research applications particularly those relating to the detection and quantification of hydrological trends at the macro scale. The selection criteria for the individual gauging stations which provide the basis for the calculation of the national and regional outflow series are discussed together with the methodology used to assess flows for the ungauged areas in each domain (here taken to include both national and regional divisions) and thence to derive a time series of total daily outflows for the post‑1960 period.