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Questions about seasonal water yield model

     I'm using seasonal water yield model to estimate ecosystem services.After learning the users's guide and some recently published articles using this model,I'm still confused about the rainfall events table that is needed to run the model.My study area is over 215000 square kilometers in extent and there are many meteorological stations within and around it,which makes the rainfall events in each month vary among different meteorological stations.Since Mesfin Sahle et al.(2019)uses the averages number of rainy days  of 12 years' daily rainfall data from eight  meteorological stations as input data for the model,I'm wondering if it's okay to use the averages number of rainy days of long term daily rainfall data from a lot of meterological stations within and around my study area to determine the rainfall events in each month.Also,are there other options to determine the rainfall events?

(the Mesfin Sahle 's article is available at


  • swolnyswolny Member, NatCap Staff
    Hi @Char -

    For an area that large, and since you have meteorological station data, you could use the Climate Zones input to Seasonal Water Yield, instead of the rainfall events. Using Climate Zones allows you to create a raster, with different zones across your study area (uniquely identified by the field cz_id), so that you can have different rainfall event data in different parts of the watershed. In your case, the different zones would be associated with different meteorological stations, and you would need to decide how to define the zones, possibly using something like a triangulation surface (but maybe better to do research on what others would recommend.)

    To use this, you also provide a Climate Zone Table, that lists the number of rainfall events per month per climate zone, matched to the raster by the cz_id field. There you can use the average long-term number of rainy days per month from your weather stations. 

    ~ Stacie
  • CharChar Member
        Thank you for your reply and great presentation at today's training.Based on the data of climate zones I have at hand,my study area is across two climate zones approximately.So I'm not sure if there is a need to futher classify the two climate zones.Moreover, the study periods of mine are fifteen years and several ecosystem services are estimated every five years, I wonder how many years of daily rainfall data is well enough for a one-year determination of rainy days per month and calculation of  water supply. Thank you and I look forward to hearing from you.
  • swolnyswolny Member, NatCap Staff
    Hi @Char -

    Cool that you're at the training - if you're there today, come up and introduce yourself, we could discuss in person.

    For the water models, usually we recommend using at least 10 years worth of rainfall data to average over, but that's a bit flexible since it's not always possible. If the services are being estimated every 5 years, perhaps the previous 5 years of data would be appropriate. @Perrine, what do you think?

    ~ Stacie
  • PerrinePerrine Moderator, NatCap Staff
    Hi Char, 
    Sorry for the late response here!
    As Stacie mentioned, the data requirements are flexible and using 5-year periods is reasonable.
    Re: climate zones, it may not be necessary to further divide your study area. This functionality was introduced for large areas, where there are distinct climate patterns. It may introduce some artificial boundaries in the outputs (at the boundary between climate zones, which is in reality more gradual). So by default, I'd suggest not to use the climate zones unless you know the number of precipitation events (not the amount of precipitation) varies dramatically across your area.
  • CharChar Member
    Thank you for your help and best wishes.
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