Watersheds in Washoe County (HUC-12) are described by tributary name and Hydrologic Unit Code 12 or HUC-12. The hydrologic unit hierarchy is indicated by the number of digits in groups of two (such as HUC 2, HUC 4, and HUC 6) within the HUC code. HUC 4 represents the subregion level, delineating large river basins. HUC 8 maps the subbasin level, analogous to medium-sized river basins; and HUC 12 is a more local sub-watershed level that captures tributary systems.