Cistern An artificial, non-pressurized reservoir filled by gravity flow and used for water storage. The reservoir may be located above, at, or below ground level. The water may be supplied from diversion of precipitation, surface, or groundwater sources. Water Infrastructure 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.