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Hello all, I am trying to find the critical oxygen deficit that can happen in a river with the introduction of a continuous waste water from a treatment plant. I have used the following parameters; Initial BOD=L= 1.471 mg/L Initial oxygen deficit = Do = 0.943 mg/L Deoxygenation Rate constant =...

7Q20 is a low flow index usually used in design of the facilities involving effluent discharge to the natural streams. It can be defined as minimum 7 day flow with a return period of 20 years. I am not clear about the 7 day thing here, i believe it has to be a moving average on daily flow data...

Can anybody tell me stepwise, how to calculate 7Q20 flow in Excel? Thanks in advance.

Can anybody tell me the difference between Rational and Modified Rational method. Lot of engineers use modified Rational Method for detention volume calcuations, is this an acceptable practice? Thank you in advance...

Thank you guys for these responses, give me enough leads....

Hi there! 1. Can 100 percent of sewer and Catch Basin volume be taken as the detention volume? 2. Normally the run off calculations are based on free flow conditions. Taking the 100 % of the sewer and CB volume would not assume that the pipes are running full and no longer under free flow...

thank you cvg and bltseattle. I am satisfied with your responses. In case Tc is longer than the storm duration, what do you recommend as a next step in modeling? should the modeling be repeated for longer storm duration or do something else?

Actually catchment areas upstream of the culverts vary from 1 hectare to about 1000 hectares. (culverts are the outlets of these catchment areas) And pavement areas are most downstream parts of these catchment areas, before outletting to the culverts. All catchment areas have Time of...

I want to challenge a statement made elsewhere as follows; Statement: In general the SWMHYMO model shows that the run off from Highway row discharges downstream before the peak flow from the external areas reaches the highway culverts. Challenge: How this statement can be made, when most Tc...

Thank you RWF for your reply. As it would appear that the drainage structures that i am dealing with are not volume sensitive. Therefore worst case scenario here would be the highest value of Peak flow. Design storm frequency i have is 50 years. So for this frequency, I wanted to know the impact...

Hi there! I wanted to know the difference in the effect of storm duration on the Peak flows. I am reading a report that has used 12 hour storm duration to do the culvert design. Catchment areas vary from less than one hectare to more than 1000 hectares. I think 12 hour storm would result in...