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Hydro Resource Evaluation Tool
physical characteristics of a hydro site
Tier 1. Transposing measured data to estimate mean flow
Transposition of flow statistics from an analogue catchment
In the UK it is common practice transposing flow statistics through rescaling by area and average annual rainfall using:
(Eq.1)
Where,
- QXT = the flow in the target ungauged site, T;
- QXA = the corresponding flow in the analogue catchment, A;
- AT = the catchment area for the ungauged site;
- AA = the catchment area for the analogue catchment;
- SAART = the Standard Average Annual Rainfall for the ungauged site;
- SAARA = the Standard Average Annual Rainfall for the analogue catchment.
Click here to estimate your proposed schemes catchment boundary area and SAAR. The gauged catchment area and SAAR are provided by the NRFA gauging station descriptions. Please note that this is an estimate of your natural flow and you will need to take account of any artificial influences within your catchment.
The uncertainties in this estimate of mean flow are dependent upon both the accuracy of the estimates of catchment area and rainfall and the similarity between your catchment and the analogue gauging station. You could complete some sensitivity testing, through changing your catchment area and rainfall to get an idea of the impact of the uncertainty of these to your mean flow estimate. Unless you have used a connected nearby gauging station and you are confident your estimates of rainfall and catchment area are accurate, then this rough estimate of mean flow should be improved upon using a regional model within Tier 2.
