Discharge Calculation help 1

[jdcivil]

Dear All,

I want to calculate the discharge at the downstream of the dam. I have the discharge and gage height just at the upstream of the dam and I have the gage height just after the downstream of the dam. I want to calculate the discharge just after the dam at downstream. Would you people suggest how can I do this because for modelling purpose I need to find discharge.

Thank you so much.

Best regards,
Jd

 

[beej67]

If the tailwater elevation is low enough so as not to influence the flow through the control structure, I would use the head-discharge relationship described by the geometry of the outlet control to approximate discharge from the dam.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[cvg]

you have really not given enough information. are you talking about a pipe outlet or a spillway? are you looking for the flow at one particular reservoir stage or the entire stage discharge relationship? what are the inlet conditions for the pipe or the spillway? Is there a weir or orifice at the inlet? Is the spillway an OGEE? Is there a channel for the tailwater?

If you have a surveyed cross section downstream of the outlet works where the flow has stabilized, you could just use Mannings equation for the normal depth.

 

[bimr]

As beej67 suggested, you need to know the geometry of the outlet control to approximate discharge from the dam.

http://www.hydroscientificwest.com/pdfs/TCCA.pdf

 

[jdcivil]

Thank you all of you for your reply.

I just checked the data from USGS. I have the gage height and discharge at the lock and dam. I am looking at Sheldon lock and dam at Blackwarrior River in Alabama.

The USGS stations that I am interested are 02466030 and 02466031.

When we have the discharge at the lock and dam, does that mean the discharge over/through dam by gates/spillways ? Thank you so much.

The link below gives the figure of the dam. I don't know exactly what type of dam is this.

http://waterdata.usgs.gov/al/nwis/uv/?site_no=02466031&PARAmeter_cd=00065,00060

Thank you so much.

 

[bimr]

Discharge should mean all flow past the dam. You can probably get the information that you want if you email them.

 

[cvg]

see link and attached file

http://water.weather.gov/ahps2/rive...22&data[]=probflow&submit=Make+my+River+Page!

 

[beej67]

Well that's a bit more complicated.

This page:

http://nwis.waterdata.usgs.gov/al/nwis/peak/?site_no=02466031&agency_cd=USGS

...doesn't have the data you need, but says to contact these guys:

http://nwis.waterdata.usgs.gov/al/nwis/feedback/?to=Alabama Water Data Inquiries

...and ask if they have it. If they don't have it, you're going to have to swag something. If you're just trying to get it in the right ballpark, you could do so by finding out what the gauge elevation of all those weirs are, and the dimensions of the weirs, and generate yourself a stage discharge relationship using the weir equation. With that, you could approximate the dam discharge for any given gauge height.

Why do you need this info anyway?

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[cvg]

whats so complicated, it's a stage - discharge graph for the dam. couldn't be much more to the point

 

[beej67]

I didn't read your post, cvg. Clearly you've got the winner there.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[3feethighandrising]

CVG-

I think you provided the wrong link. The link you provided was for probalistic future flows based on data from 5/9/11, it is not recorded stage/discharge flows.

 

[cvg]

it is plotted on a graph which shows the stage/discharge values. who cares what the probalistic flows are.

for example, looking at my pdf I can read of the following selected stage discharges from the the graph.

stage flow
81.29 ft 17,004 cfs
86.03 ft 27,996 cfs
91.05 ft 39,988 cfs (flood stage)
105.0 ft 104,940 cfs (major flooding)