Mean flow calculation for hydro scheme
Mean flow calculation for hydro scheme
(OP)
I am undertaking a feasibility study for a hydro scheme in the UK. We have daily flow records for the last 40 years from a gauging station about 13Km downstream. Using the FEH CDI have SAAR, SPRHOST, AREA values ect. for the site and gauging station. The gauging station catchment area is about 50% greater than the site's catchment.
I have calculated the average flow rate at the gauging station (m3/s) from the daily flow records.
My question is how can I translate this flow rate at the gauging station to that at the site?
Any assistance in this would be greatly appreciated.
I have calculated the average flow rate at the gauging station (m3/s) from the daily flow records.
My question is how can I translate this flow rate at the gauging station to that at the site?
Any assistance in this would be greatly appreciated.





RE: Mean flow calculation for hydro scheme
RE: Mean flow calculation for hydro scheme
RE: Mean flow calculation for hydro scheme
As you can imagine, complex computer models are available for more accurate estimates... but they require a lot of data which is an extensive effort to gather.
With the rational method, runoff (Q) is directly proportional to the factors used to make the calculations. In other words, Q is proportional to the land area (A), and the rainfall intensity (i). So, in your case, you would be justified in simply using the stream gauge data you have and reducing that number proportionate to the smaller watershed area and increasing the annual rainfall rate. [Are your watersheds so far apart that the SAAR is different for each watershed? If yes, then a more rigorous analysis seems to be needed.]
If you decide to dive deeper into the calculations, then first try to get a method that accurately predicts the annual runoff to the gauging station. In other words, use the gauging station data to calibrate your assumptions. Then you have some good numbers to use to do calculations on the smaller watershed.
Ok, that's a start - but just the tip of the iceberg compared to the complexities involved.
RE: Mean flow calculation for hydro scheme
Perhaps a better method is to get some flow data from your proposed site and correlate it to your downstream gage. This would be far better than any desktop method.
RE: Mean flow calculation for hydro scheme
Many thanks for your help on this.
Ben,
The SAAR and SPR do vary slightly.
What you suggested confirms what I had originally planned:
Q1/(A1xSPR1xSAAR1)=Q2/(A2xSPR2xSAAR2)
CVG
I reconise that this is a very simplistic approach but the flow calculation is for a feasibility study not detailed design so is only an estimate.
RE: Mean flow calculation for hydro scheme
RE: Mean flow calculation for hydro scheme
Dik
RE: Mean flow calculation for hydro scheme