Good question..........Have often wondered how long it would take to get the current moving around 68 bridge after the generation flow picks up at the dam. When the flow begins at dam it takes awhile before the river swells miles downstream.....would think the same (in reverse) would hold true above the dam too. Seems it would take awhile before the water would start moving "uplake" as well. Seems like the flow just above the dam would be somewhat immediate....and the farther "uplake" you go it would be delayed. Doesn't this seem logical ?