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All Topics | Topic "Difference between surface runoff and streamflow in WEAP results."
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Author Message
Dr. Mohammad Merheb

Subject: Difference between surface runoff and streamflow in WEAP results.   
Posted: 7/14/2021 Viewed: 305 times
I have a question regarding the model results. In WEAP results you can obtain a variable called surface runoff and you can also obtain another variable called streamflow.
From what i am obtaining as results, the values of these 2 variables are quite different even when comparing streamflow at the outlet of the basin.
When comparing to observed streamflow values, the surface runoff result is quite different, however, i was able to adjust the simulated streamflow by using observed headflows since i know that the river i am modelling is mainly a spring fed river.
So, i have assumed that the surface runoff refers to the direct runoff of the river, aka the runoff that results directly form rainfall input, while the streamflow is the direct runoff + any given baseflow.
Is my assumption correct?
I could not find a response in the WEAP literature, the majority of published works use the term streamflow ambiguously so i was not able to know if they are referring to the streamflow or the surface runoff (this variable is a part of the water balance components). So i am not sure if i should calibrate my model against the surface runoff (compare the observed streamflow to surface runoff) or should i calibrate against the streamflow?
Ms. Anne Hereford

Subject: Re: Difference between surface runoff and streamflow in WEAP results.   
Posted: 7/16/2021 Viewed: 262 times
Dear Mohammad,
In short, yes, your assumption is correct. Runoff (for the Soil Moisture Method) includes surface runoff, direct runoff (only if z1 > 100%), interflow and base flow. See the diagram on https://www.weap21.org/WebHelp/Two-bucket_Method.htm
It is related to precipitation, but will vary from the precipitation volume based on the hydrological parameters your model is using (evapotranspiration, infiltration, etc).
Streamflow at a given node in your model will include streamflow from the previous node plus any inputs (surface runoff, return flows from demand sites, +/- exchange with groundwater) and outflows (withdrawals for demand sites, etc)
The use of "streamflow" in the literature should be interpreted as the volume of water per unit time that is passing through the referenced point on the river. Your observed streamflow data should be compared to WEAP's "streamflow" results when calibrating your model.

Topic "Difference between surface runoff and streamflow in WEAP results."