My question is conceptual: if the Water Yield model produces an annual result for a given reference year (e.g., 2025), why does the documentation strongly recommend using at least 10 years of precipitation and evapotranspiration data, and ensuring that these climatic inputs “match” the land use map date? In practice, does the model represent a specific year, or rather a long-term average hydrological condition associated with a given land use configuration? I would appreciate clarification on how to correctly interpret the temporal meaning of the model outputs.
Hi @Fernbg77,
The Annual Water Yield model was made to represent long-term annual average water production. This thread contains a discussion of the precipitation, ET0, and LULC rasters that you may find helpful, and this thread goes into additional detail regarding the 10-year recommendation.
You may also find the User’s Guide sections on calibration, precipitation, and evapotranspiration helpful, if you haven’t yet seen them.
In practice, does the model represent a specific year, or rather a long-term average hydrological condition associated with a given land use configuration?
The model represents the latter - a long-term average hydrological condition associated with a given land use configuration. This is consistent with the simple methods behind the model calculations. So the results represent the average annual water yield across all of the years that you use to create the model inputs. One of the effects of this is that changes in land use/land cover are apparent, and the model can be used to focus on how changes in land use may affect the average water flow conditions.
~ Stacie