About the GROW Water Planner

Use the GROW Water Planner at www.waterplanner.growobservatory.org

Use the GROW Water Planner to find out how much water your plants will need over the coming months, based on your location.

Please note, the tool is a prototype and only contains limited data around the following locations: Greece (Evros & Laconia), Ireland, Hungary (Miskolc), Spain (Barcelona), Portugal (Lisbon), Scotland (Tayside & Central belt), Austria (Vienna), Netherlands (’s-Hertogenbosch), Luxembourg

What does this app do?

This tool is intended to support your water planning and management. It can help you determine how well you can grow in your climate. It is best used alongside observations of your site and plants.

How is this water estimate calculated?

The calculation uses temperature and precipitation data from Agri4cast and combines it with the average water demands of 10 commonly grown crops. The Agri4cast data is weather data from across Europe and is calculated for 25 km grid squares.
When you choose a location, the calculation takes into account the water availability from the climate of the grid square for your location and combines that with the water uptake of the plants from soil. It can then identify the likely water deficit or surplus required for growing at that site each month.

Assumptions behind this estimate

Here we show an estimated amount of water for your plot size in your location based on real monthly averages of temperature and rainfall. The exact amount of water required will of course depend on the number and type of plants in the space, and your actual rainfall.
As a guide, this estimation would be most accurate for plants such as grass, maize, potato and beets with around 7 (maize) to 100 (grass) plants per square metre.

Water-thirsty plants such as cabbage, peppers, celery, or watermelon are likely to need more water than estimated here. More drought-tolerant plants such as onions, beans, and garlic are likely to need less.

Also short-term plants such as radish, lettuce, green peas can be better positioned within the parts of the year with enough water, whereas long-term plants like carrots, cabbage or maize can be more affected by shortage of water and less flexible in planting and harvesting dates.

How do we define a dry year and a wet year?

We have produced data for an ‘average’ dry or wet year by taking the driest and wettest years over the past 20 years and averaging them.
We classified years accordinging to the SPEI drought index used by climatologists to estimate abnormal drought incidence. It compares theoretical demand of plants for water (so-called evapotranspiration) and the rainfall which can fulfill this demand during the same period of time.
Drought is normal in many regions. SPEI is therefore calculated and expressed as a statistical measure for showing a shift of actual climate conditions from the normal ones (average). We considered values of SPEI 2 or – 2 as calculated for vegetation season over the last 20 years as indicative of ‘wet’ or ‘dry’ years, respectively. All other years were considered as ‘normal’.

Other considerations

Soil texture can influence how water is retained in your soil. Sandy soils will drain water more quickly and may require more frequent additions of water in dry weather. Clay soils are more prone to becoming water-logged and less likely to require additional water.

Who developed this tool?

The scientific calculations behind this tool were developed by Dr. Rastislav Skalsky, a Research Scholar from the International Institute for Applied Systems Analysis (IIASA) in Vienna.

Additional input was provided by Dr N. K. van der Velden, Senior Researcher in Agroecology at the Permaculture Association (Britain).

What else can I do to improve my soil and its ability to retain water?

There is a lot you can do to improve the condition of your soil. Take a look at GROW’s info sheets about regenerative food growing practices.

Updated on 31st October 2019

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