Centerlines of mainstem stream digitized at 1:15,000 or better. Begins at the study dam and continues approximately 200 miles or until the river reaches a confluence of another river of sufficient size as to absorb the flow. Centerlines digitized from Aerial Photography are indicatd with Meta_ID field value "CWMS Mapping". Centerlines provided by the district to be used as is are indicatd with Meta_ID field value "District Source". Additional tributary centerlines digitized at varying scales sufficient to accurately capture features.