CatchmentsUK
CatchmentsUK enables you to define catchment boundaries quickly and reliably, using digital terrain data for Great Britain. (note this excludes Northern Ireland)
The GIS interface of CatchmentsUK enables catchment outlets and boundaries to be verified using supplied digital maps or imported contextual data.
The boundaries can be exported as CSV files or Esri shapefiles for use in a wide range of applications, including LowFlows 2.