Source: Rainwater Harvesting Group, http://rainwaterharvesting.tamu.edu
Rainwater harvesting calculators are important for several reasons. They help to better balance the supply and demand so that a system can be sized correctly and so the user has adequate storage to get through long periods without rainfall. There are countless rainwater harvesting calculators available on the internet. The calculator included below was developed by the Texas A&M AgriLife Extension service. It allows the user to determine stored water volume over the course of three years and whether supplemental water is needed.