Muskingum Routing equation

[chicopee]

The sum of the coefficients C(0), C(1) and C(2) turns out to be one which is consistent with for this routing equation. However, my coefficient C(0)is a negative value, for my delta T of 2 hours. Is it alright to have a negative coefficient or should I increase my delta T in order to have all positive coefficients?

 

[RWF7437]

What are you trying to do ? There's probably an easier way than working the Muskingum Routing by hand calculation. And, are you certain this is the correct routing to be using ?

good luck

 

[chicopee]

Yes, to the routing procedure as all my references point to that direction. Based on an inflow hydrograph, Manning velocity equation for flow velocities, channel section discharge rates relationships to channel cross sectional areas, time step selections, and miscellaneous parameters, my outflow hydrograph over a dam crest shows a dip in the negative flow rate( vertically plotted)due to the negative value of C(0). I can correct this dip by increasing my time step from 2hrs to 6 hrs however this will affect the shape of my outlfow hydrograph. I am investigating a flooding condition of a low land section along the Housatonic River

 

[chicopee]

To RWF7437- Researching the cause of the dip in my ouflow graph is a side effect according to my references so I am no longer concerned about; Nonetheless my original question still remains should my coefficient C(0) be a negative value eventho my outflow hydrograph shows a peak lag of 28.5 hrs and some attenuation ( peak ratio of 5300 cfs/6100cfs) which I would expect for the area in question.

 

[francesca]

It has been a year now and I have thrown my notes away, but I believe that negative coefficients are not a problem and that the acid test is if the sum of your coefficients is 1. I also believe that the Muskingham-Cunge routing method is one of the more robust and is certainly the one we used in our class analysis of a dam. It is included in WMS and PondPack.

From the Tooele County General Plan (courtesy of Google):

Generally, the Muskingham-Cunge Method is the preferred technique for master planning purposes. This technique allows the user to de?ne either a channel or conduit cross-section along with a Manning ‘n’ value. The routing is utilized to account for hydrograph attenuation due to travel time and the in?ow hydrograph. This method does not account for backwater, ?ows exceeding the conduit capacity or pressure ?ow.

 

[chicopee]

Thanks for your reply Francesca. I somewhat suspected the same thought and after plotting the outflow which looked pretty good you confirmed my thinking.