Calculator: Rainwater collection and evaporation from reservoirs
To estimate the amount of rainwater that can be captured, we need to know the normal climatological values, in particular, the average annual rainfall which is measured in millimeters (equals to liters per square meter).
If there is no exact local value, in Spain, for instead, we can get an approximation from the Meteorological Agency. After selecting the location, precipitation appears in the column marked with letter R.
Once you're there, you can record the value of mean annual temperature (the column bellow T) that will be used to estimate the evaporation.
In addition, we have to know the collecting surface (roof, parking, pool, sporting court...), the height above sea level and the storage reservoir surface area (for uncovered ones).
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