ESRI Shapefile format
The catchment boundaries have been digitised from scanned topographic maps of Plynlimon Catchment Areas. The source of the sub-catchments boundaries is unknown but must have also being digitised, most likely from hand-drawn boundaries on scanned maps. The topographic maps reference are: Plynlimon Catchment Areas - Severn Catchment. Sheet No. 1. Scale 1:5000. Wallingford, Berkshire. Institute of Hydrology, Natural Environmental Research Council, 1968. Plynlimon Catchment Areas - Wye Catchment. Sheet No. 2. Scale 1:5000. Wallingford, Berkshire. Institute of Hydrology, Natural Environmental Research Council, 1968. Plynlimon Catchment Areas. Sheet No. 1. Scale 1:10000. Wallingford, Berkshire. Institute of Hydrology, Natural Environmental Research Council, 1968
