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SWY validation

I run SWY model for a mountain river basin in Northern Italy. I have discharge data for several years at different sampling points. Can I use these data to validate the outcome of the model? if yes, which output raster should I consider?


  • PerrinePerrine Moderator, NatCap Staff
    Hi Mattias, 

    Great that you have discharge data at several locations.
    As a first step, you need to extract the baseflow from your flow time series (there are baseflow separation filters available in many statistical software packages).
    Then, I'd recommend looking at the subwatershed Qb values (in the output shapefile), rather than the raster values. This is because the flow data are aggregated measures of flow (across the subwatershed area). These areas should correlate with your observed baseflow values.

    Does the work flow make sense? Let me know if you have questions about this.

  • JaraJara Member
    Hi Perrine,

    Following up on this question from October 2018 about how to validate the SWY model. I'm quite confused with the different output names/ terminology, and would appreciate if you can clarify some doubts for me please. 

    I am running the SWY model using average precipitation and ETo for the period 2007-2017. For validating the results, I have discharge data for the same period. I should then compare the Qb values with the observed data I have, however, I'm getting confused with the following: 

    My questions are:

    1) I have discharge data available in  cubic metres per second (Cumecs), megalitres/day, or  megaliters per month or megaliters per year. What would be the best variable to use for comparing to the Qb values from the shapefile output?

    2) What are the units of the  Qb values? I understand they are mm/pixel, but is this value reflecting the aggregated sum of the number of pixels in  watershed z  on an annual time scale?  

    3) If the answer to the second question is "yes" then I'm guessing the best approach for my validation is to use the megaliters p/year observed data to compare it to the Qb values (previous conversion of units). Please let me know if this makes sense to you, or please correct me if I'm getting things wrong.

    4) In your comment from October 2018 to Mattias, you mentioned the need to "extract the baseflow from the flow time series" where you referring to the observed discharge data? if that is the case, can you point out one statistical software package as an example? Just for extra information, this is the definition of discharge from the data that I'm using:

    Hydrology commonly deals with discharge, also known as a flow rate, which is expressed as a volume of water passing by a point within a particular time-frame, e.g. the discharge or flow rate at a Gauging Station may be 250 m3/sec.

    5) I have the area comprising each of the gauges, but I dont have a shapefile delineating each of the catchments. What do you recommend me for trying to match the geometry and area of the observed data vs the model outputs (i.e. comparing both catchments)? 

    Thank you so much in advance and my apologies for such a long question!

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