Mankato, MN rainwater: 28,931 gallons off a roof
How much rain a roof in Mankato, MN collects
28,931gallons a year
That is a 1,500 sq ft asphalt roof under Mankato, MN's normal 36.4 inches of rain, about 795 gallons for every inch that falls.
In Mankato, MN 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 Mankato 1.5 Se station (1.4 mi away). Mankato, MN ranks 2nd wettest of the 103 cities covered in Minnesota.
Month by month in Mankato
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 1.19 | 946 | |
| Feb | 0.99 | 787 | |
| Mar | 1.99 | 1,582 | |
| Apr | 3.61 | 2,869 | 92 |
| May | 4.42 | 3,513 | |
| Jun | 5.37 | 4,268 | |
| Jul | 5.07 | 4,030 | |
| Aug | 3.95 | 3,139 | 50 |
| Sep | 3.79 | 3,012 | 70 |
| Oct | 2.80 | 2,225 | 193 |
| Nov | 1.65 | 1,311 | |
| Dec | 1.57 | 1,248 |
Jun is the wettest month (5.37 in, 4,268 gal off the roof); Feb the driest (0.99 in). Garden shortfall is what a 200 sq ft vegetable bed needs beyond the rain that lands on it, April to October.
Barrel or cistern in Mankato?
Best fit: one 55-gallon barrel, which delivers about 331 gallons to the garden in a normal year (81.7% 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 Mankato's roof water will pass straight through it.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 331 | 27,640 |
| 110 gal | 331 | 27,640 |
| 165 gal | 331 | 27,640 |
| 275 gal | 331 | 27,640 |
| 550 gal | 331 | 27,640 |
| 1,000 gal | 331 | 27,640 |
| 1,500 gal | 331 | 27,640 |
| 2,500 gal | 331 | 27,640 |
| 5,000 gal | 331 | 27,640 |
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 Minnesota?
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