I used a diversion from a basin to direct the spillway to a swale that feeds a second basin. I’m getting oscillation in the resulting hydrographs (32-33) and a negative volume under the hydrograph and negative flows on the descending limb that carries through to the subsequent hydrographs. I decreased my time interval to 1 minute. No change. The split as far as rate looks good. I’m thinking because the diversion has no area it doesn’t generate a volume for the hydrograph (…worse it generates a negative volume). However when it gets to the second basin the peak inflow reported is correct and the basin routing also looks accurate.
Is there anything I can do to get rid of the oscillation? Is it a problem?
Also the diversion hydrograph reports the same peak rate, etc. until you make a report…then it correctly assigns the peaks. Is this normal?
Update. I asked a local user of Hydroflow. The oscillation occurs when I divert the primary discharge pipe (which in reality is the discharge that is being pealed off to a combined system). He recommended me switching the diversion to identify the emergency spillway (Weir B) and then do the combination of the appropriate leg of the diversion with the subsequent hydrographs (through a connecting swale and to a second basin). I attached both the original and the revised so you can see the difference. It appears that the pipe/orifice calculations combined with the diversion is unstable. See if I went wrong elsewhere.