Half-Hourly Precipitation and Streamflow, River Hirnant, Wales, U.K., November and December, 1972

The Hirnant subcatchment of the River Dee has an area of 33.9 km2 and is situated west of Bala Lake in North Wales. Impervious rocks, providing very little storage for rainfall, combine with steep slopes to give a fast streamflow response to rainfall. The river is gauged at Plas Rhiwaedog at a natural river section, to provide discrete time streamflow data at half hourly intervals. The precipitation data consists of estimates of a real rainfall derived from six recording rain-gauges situated in and around the catchment. The present set of data, Table 14.1, is part of several years’ data on the Hirnant and other subcatchments of the Dee collected and available at the Welsh Water Authority and at the Institute of Hydrology, Wallingford, U.K. The hydrolic control is a natural rock outcrop and is subject to minor changes from year to year. A real-time flow forecasting system has been operational on the River Dee since 1975 as part of extensive water supply and flood control schemes for the catchment.