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# WaterPod rainwater calculations

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The WaterPod will be collecting rainwater from a few of the impermeable roof areas. The calculations for collection are on this spreadsheet. There are three tabs feeding the results:

• Tab:Collection Calcs - Calculates the monthly availability of the rainwater.
• Tab:Collections Dimensions - Calculates the available rainwater collection area based upon the planned structures.
• Tab:Regional Climate Data - Show monthly rainfall from historical averages. Could be made more current.

## Regional Climate Data

The historical 1971 - 2000 Rainfall Normals for Central Park, New York[1] are:

 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual 3.42 3.27 4.08 4.2 4.42 3.67 4.35 4.01 3.89 3.56 4.47 3.91 47.25

## Basic Calculation

$Collection\ Volume (gal) = Rainfall\ (in) \times \frac{1 ft}{12 in}\times Collection\ Area\ (ft^2) \times \frac{7.48 gal}{ft^3} \times Roof\ Coefficient \times Efficiency$

or

$V=R \times A\times k \times e$

(in some cases the efficiency of the system is assumed to be 100% and therefore equal to 1, having no effect on the rest of the equation.)