How to calculate 7Q20 1

[salhu]

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

Thanks in advance.

 

[RWF7437]

What on Earth is 7Q20 ??????

 

[gbam]

Yes, Please Explain 7Q20.

 

[sam74]

I've never heard of it but you can do a google search on "7Q20 storm water flow spread sheet" and get several hits but no spread sheet.

 

[salhu]

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 values.

 

[RWF7437]

Try this link:

http://www.trentu.ca/wsc/PDFfiles/LowFlowOntRpt2004.pdf

good luck

 

[queque]

The 7Q10 is the seven day low flow with a recurrence interval of ten years. The USGS publishes this for areas throughout the US.
Call the USGS District office in your State and speak with the District Surface Water Specialist. He can provide you with the value and the error associated with that value.