Bemidji, MN rainwater: 21,865 gallons off a roof
Rainwater from a roof in Bemidji, MN
21,865gallons a year
That is a 1,500 sq ft asphalt roof under Bemidji, MN's normal 27.5 inches of rain, about 795 gallons for every inch that falls.
In Bemidji, 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 Bemidji station (4.2 mi away). Bemidji, MN ranks 99th wettest of the 103 cities covered in Minnesota.
Month by month in Bemidji
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 0.74 | 588 | |
| Feb | 0.79 | 628 | |
| Mar | 1.16 | 922 | |
| Apr | 1.89 | 1,502 | 307 |
| May | 3.06 | 2,432 | 161 |
| Jun | 4.49 | 3,569 | |
| Jul | 3.96 | 3,147 | 49 |
| Aug | 3.25 | 2,583 | 137 |
| Sep | 3.05 | 2,424 | 162 |
| Oct | 2.65 | 2,106 | 212 |
| Nov | 1.41 | 1,121 | |
| Dec | 1.06 | 842 |
Jun is the wettest month (4.49 in, 3,569 gal off the roof); Jan the driest (0.74 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 Bemidji
Best fit: one 55-gallon barrel, which delivers about 829 gallons to the garden in a normal year (80.7% 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 Bemidji's roof water will pass straight through it.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 829 | 20,121 |
| 110 gal | 829 | 20,121 |
| 165 gal | 829 | 20,121 |
| 275 gal | 829 | 20,121 |
| 550 gal | 829 | 20,121 |
| 1,000 gal | 829 | 20,121 |
| 1,500 gal | 829 | 20,121 |
| 2,500 gal | 829 | 20,121 |
| 5,000 gal | 829 | 20,121 |
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