The longitudinal output displays simulation results from all the river segments in the selected reach. The X-axis has river miles calculated from the length of each river segment. The results for flow, hydrologic properties (such as velocity), temperature, and chemical constituents are all shown strictly for the date shown. Travel time is calculated from the length of each river segment and the flow velocity. Travel time calculations take into account the time lag as the water flows downstream. Working upstream from the downstream end of the reach, once the travel time exceeds one day, the calculation of travel time uses velocity output from the previous simulation day. This looking backward in time continues for each whole day in travel time.