# Conceptual doubt **URL:** \ **Category:** Software Support\ **Tags:** annual-water-yield\ **Created:** [January 18, 2026, 1:33am UTC](https://community.naturalcapitalalliance.org/t/conceptual-doubt/6325 "2026-01-18T01:33:32Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Fernbg77](https://yyz1.discourse-cdn.com/flex031/user_avatar/community.naturalcapitalalliance.org/fernbg77/32/3769_2.png) [@Fernbg77](https://community.naturalcapitalalliance.org/u/Fernbg77)\ **Post date:** [January 18, 2026, 1:33am UTC](https://community.naturalcapitalalliance.org/t/conceptual-doubt/6325/1 "2026-01-18T01:33:32Z")
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. ---
**Author:** ![megannissel](https://yyz1.discourse-cdn.com/flex031/user_avatar/community.naturalcapitalalliance.org/megannissel/32/3547_2.png) [@megannissel](https://community.naturalcapitalalliance.org/u/megannissel)\ **Post date:** [January 20, 2026, 9:02pm UTC](https://community.naturalcapitalalliance.org/t/conceptual-doubt/6325/2 "2026-01-20T21:02:29Z")
Hi @Fernbg77, The Annual Water Yield model was made to represent long-term annual average water production. [This thread](https://community.naturalcapitalalliance.org/t/about-the-average-annual-rainfall-data-in-the-water-yield-module/2431) contains a discussion of the precipitation, ET0, and LULC rasters that you may find helpful, and [this thread](https://community.naturalcapitalalliance.org/t/period-of-precipitation/5761) goes into additional detail regarding the 10-year recommendation. You may also find the User’s Guide sections on [calibration](https://storage.googleapis.com/releases.naturalcapitalproject.org/invest-userguide/latest/en/calibration_freshwater.html#calibrating-the-invest-freshwater-models), [precipitation](https://storage.googleapis.com/releases.naturalcapitalproject.org/invest-userguide/latest/en/data_sources.html#precipitation), and [evapotranspiration](https://storage.googleapis.com/releases.naturalcapitalproject.org/invest-userguide/latest/en/data_sources.html#evapotranspiration) helpful, if you haven’t yet seen them. ---
**Author:** ![swolny](https://yyz1.discourse-cdn.com/flex031/user_avatar/community.naturalcapitalalliance.org/swolny/32/181_2.png) [@swolny](https://community.naturalcapitalalliance.org/u/swolny)\ **Post date:** [January 20, 2026, 9:28pm UTC](https://community.naturalcapitalalliance.org/t/conceptual-doubt/6325/3 "2026-01-20T21:28:15Z")
> 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 ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex031/uploads/naturalcapitalproject/original/2X/8/8d95591aa074da87ea0fdd61ca47c1c3c0588aa7.png) [@system](https://community.naturalcapitalalliance.org/u/system)\ **Post date:** [April 20, 2026, 9:28pm UTC](https://community.naturalcapitalalliance.org/t/conceptual-doubt/6325/4 "2026-04-20T21:28:57Z")
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