Spring A location at which the water table intersects the land surface, resulting in a natural flow of groundwater to the surface. Springs may be perennial, intermittent, or ephemeral. Spring Sites Adapted from USGS Site Types. http://wdr.water.usgs.gov/nwisgmap/help/sitetype.html ODM2 SiteType Controlled Vocabulary ODM2 Working Group A vocabulary for describing the type of a data collection Site. To some extent, these types represent the ultimate feature of interest that the site was established to measure. For example, a Stream Site was established to measure properties of a Stream.