Grand Rapids, MN rainwater: 23,351 gallons off a roof
How much rain a roof in Grand Rapids, MN collects
23,351gallons a year
That is a 1,500 sq ft asphalt roof under Grand Rapids, MN's normal 29.4 inches of rain, about 795 gallons for every inch that falls.
In Grand Rapids, 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 Grand Rpds Forest Lab station (1.7 mi away). Grand Rapids, MN ranks 88th wettest of the 103 cities covered in Minnesota.
Month by month in Grand Rapids
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 0.97 | 771 | |
| Feb | 0.85 | 676 | |
| Mar | 1.33 | 1,057 | |
| Apr | 2.10 | 1,669 | 281 |
| May | 3.23 | 2,567 | 140 |
| Jun | 4.70 | 3,736 | |
| Jul | 4.14 | 3,290 | 26 |
| Aug | 3.40 | 2,702 | 118 |
| Sep | 3.05 | 2,424 | 162 |
| Oct | 2.79 | 2,218 | 194 |
| Nov | 1.59 | 1,264 | |
| Dec | 1.23 | 978 |
Jun is the wettest month (4.70 in, 3,736 gal off the roof); Feb the driest (0.85 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 Grand Rapids?
Best fit: one 55-gallon barrel, which delivers about 744 gallons to the garden in a normal year (80.8% of its need).
If you set one up, a 55-gallon barrel with a downspout diverter is the whole job. Check that the overflow points away from your foundation, because most of Grand Rapids's roof water will pass straight through it.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 744 | 21,662 |
| 110 gal | 744 | 21,662 |
| 165 gal | 744 | 21,662 |
| 275 gal | 744 | 21,662 |
| 550 gal | 744 | 21,662 |
| 1,000 gal | 744 | 21,662 |
| 1,500 gal | 744 | 21,662 |
| 2,500 gal | 744 | 21,662 |
| 5,000 gal | 744 | 21,662 |
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