Annual available water web map on ArcGIS Online

by Daniel Siegel, Product Engineer, Esri

Available WaterIn order to better understand the global distribution of water resources, Esri’s Mapping Center has produced a map of average annual available water for the entire non-polar land surface.  If precipitation is income, evapotranspiration is a tax.  Everything else – fish, people, aquifer recharge, etc. has to share the available water left over after evapotranspiration has taken its share.  Different regions have very different rates of evapotranspiration, which means that those which get more rain do not necessarily have more water available for use.

The average annual available water map was built using precipitation data from WorldClim and evapotranspiration data from the MOD16 Global Evapotranspiration Product.  Both datasets have one kilometer resolution, but the latter is not valid over urban or barren land, so available water is not calculated for these areas.  Hydrography from the World Hydro Reference Overlay is included to show the path runoff will take over the landscape.  In order to highlight the central roll topography plays in directing the flow of water, the No Alteration of Grayscale or Intensity (NAGI) method was used to combine this map with an elevation hillshade.  Click anywhere on the map and a pop-up window shows the available water as a fraction of precipitation.

Available Water with Pop-up

Use this map map as a canvas for your own observational data.

You can also access the services that make up the map:

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Leave a Reply


  1. geo-elektrika says:

    Excellent presentation. Thanks for this.

    You wote:

    “it can be stored in lakes, soil moisture, and underground aquifers, abstracted by humans,”

    Did you mean extracted? If not, please tell me more about what abstraction means in the hydrology context. I found nothing related at


    • daniel.siegel says:

      Glad you like the map, and thanks for the feedback. “Abstract” can mean “to divert or take away,” and is often used this way in hydrology, but I have removed the word to avoid unnecessary jargon. Hope it reads more clearly now!

      • geo-elektrika says:

        Jargon opens the door to learn something new. Glad for the vocab lesson. Thanks for this.
        I was an English major once … long ago … before Jack and Roger invented GIS. ;-)

  2. cb0224 says:

    Is anyone else having trouble viewing the application? I don’t know if the services were blocked b/c I’m viewing from a government computer but the application only loaded the frame, no services, no map.

  3. tomdilts says:

    This is a wonderful product but I have to think that it is a bit misleading, particularly in boreal and tropical regions. Was average annual available water calculated as cumulative annual precipitation minus cumulative annual evapotranspiration? If so then this can lead to misleading results because it doesn’t account for the timing of precipitation and evapotranspiration. For example, I used to live in Fairbanks Alaska and I currently live in Reno Nevada. Both of which show up as arid. Reno is really arid, but Fairbanks is very green in the summer. In Fairbanks there is plenty of precipitation in the summer when the evapotranspiration demand is high, but very little in the winter when the demand is low. I suspect that something similar is happening in the Yucatan Peninsular of Mexico and other tropical regions that have distinctive wet vs. dry seasons.