Madison, IN rainwater: 40,519 gallons off a roof
Madison, IN: gallons off the roof each year
40,519gallons a year
That is a 1,500 sq ft asphalt roof under Madison, IN's normal 51.0 inches of rain, about 795 gallons for every inch that falls.
In Madison, IN a single barrel does most of the work. Storms come often enough that a small tank refills before it runs dry, and a bigger one would mostly sit full.
Rainfall: NOAA 1991-2020 climate normals, the Madison Sewage Plt station (1.5 mi away). Madison, IN ranks 4th wettest of the 88 cities covered in Indiana.
Month by month in Madison
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 3.47 | 2,758 | |
| Feb | 3.15 | 2,504 | |
| Mar | 4.47 | 3,553 | |
| Apr | 5.54 | 4,403 | |
| May | 5.37 | 4,268 | |
| Jun | 4.97 | 3,950 | |
| Jul | 4.81 | 3,823 | |
| Aug | 4.23 | 3,362 | 15 |
| Sep | 3.53 | 2,806 | 102 |
| Oct | 3.63 | 2,885 | 90 |
| Nov | 3.61 | 2,869 | |
| Dec | 4.20 | 3,338 |
Apr is the wettest month (5.54 in, 4,403 gal off the roof); Feb the driest (3.15 in). Garden shortfall is what a 200 sq ft vegetable bed needs beyond the rain that lands on it, April to October.
What size rain barrel for Madison
Best fit: one 55-gallon barrel, which delivers about 170 gallons to the garden in a normal year (82.1% of its need).
Before you buy, a 55-gallon barrel with a downspout diverter is the whole job. Check that the overflow points away from your foundation, because most of Madison's roof water will pass straight through it.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 170 | 39,060 |
| 110 gal | 170 | 39,060 |
| 165 gal | 170 | 39,060 |
| 275 gal | 170 | 39,060 |
| 550 gal | 170 | 39,060 |
| 1,000 gal | 170 | 39,060 |
| 1,500 gal | 170 | 39,060 |
| 2,500 gal | 170 | 39,060 |
| 5,000 gal | 170 | 39,060 |
Simulated storm by storm through a normal year using the station's count of days with 0.1 in or more of rain each month.
Is rainwater collection legal in Indiana?
No statewide rainwater harvesting regulations; check county for local incentives
From the 2015 (Pacific Northwest National Laboratory report 24347); not yet re-checked against current law, so check with your state water agency before building anything large. Source