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OS MasterMap Water Network Layer is a detailed, heighted water network, showing the flow and course of every river, stream, lake and canal in Great Britain.

The vector link and node network provides a detailed centre line following the curve of the waterway and includes coordinates of watercourse sources and where they meet (with flow direction, gradient, length and width anywhere along its length). The product also illustrates underground watercourses (inferred from entry and exits), details the heights of watercourses in relation to sea level and provides TOID and Environment Agency or Scottish Environment Protection Agency catchment name and ID. OS MasterMap® Water Network Layer is useful in 2D and 3D modelling for planners, surveyors and engineers.