Description: GRTS locational data for nonpoint source projects. GRTS locations are coded onto NHDPlus v2.1 flowline features to create point and line events or coded onto NHDPlus v2.1 waterbody features to create area events. In addition to NHDPlus reach indexed data there may also be custom events (point, line or area) that are not associated with NHD and are in an EPA standard format that is compatible with EPA's Reach Address Database. Custom events are used to represent GRTS locations that are not represented well in NHDPlus.