Gage Gap Analysis (View)

This layer shows California flowlines and their status with respect to stream gage coverage. The Gage Gap Analysis is part of the Senate Bill 19 Stream Gaging Plan, which seeks to identify and prioritize areas for additional stream gaging efforts. The stream gage dataset is a snapshot of gages from the fall of 2020, consisting only of USGS and CDEC gages. The flowlines dataset is based on the National Hydrography Dataset (NHD) Medium Resolution Version 2.1 and associated Value-Added Attributes. Modifications include adding and removing attributes from the base dataset and filtering to remove flowlines that lack information on upstream drainage area, nearly all infrastructure and coastline flowlines, and flowlines under large waterbodies. Finally, attributes that designate the gage coverage and gap status (Gage Gap Analysis) were added to every flowline. A flowline is considered covered (or gaged) if its upstream drainage area is greater than 50% and less than 150% of a stream gage as a stream gage directly downstream or upstream. Data Dictionary: Field Name Range Description comid Common identifier of an NHDFlowline feature gagegap_status indicates if the stream segment is well-gaged, almost well-gaged, inactive gage, or never gaged gage_comid comid of the gage that covers this steam segment (if any) site_id site_id of the gage that covers this steam segment (if any) drainage_area_sqkm drainage area upstream of this stream segment, in sqkm stream order 0 - 9 Modified Strahler Stream Order