Cottage Grove, MN rainwater: 26,491 gallons off a roof
Rainwater from a roof in Cottage Grove, MN
26,491gallons a year
That is a 1,500 sq ft asphalt roof under Cottage Grove, MN's normal 33.3 inches of rain, about 795 gallons for every inch that falls.
In Cottage Grove, 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 Hastings Dam 2 station (4.3 mi away). Cottage Grove, MN ranks 33rd wettest of the 103 cities covered in Minnesota.
Month by month in Cottage Grove
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 0.90 | 715 | |
| Feb | 0.91 | 723 | |
| Mar | 1.78 | 1,415 | |
| Apr | 3.10 | 2,464 | 156 |
| May | 4.33 | 3,442 | 2 |
| Jun | 4.94 | 3,926 | |
| Jul | 4.37 | 3,473 | |
| Aug | 4.23 | 3,362 | 15 |
| Sep | 3.21 | 2,551 | 142 |
| Oct | 2.61 | 2,074 | 217 |
| Nov | 1.72 | 1,367 | |
| Dec | 1.23 | 978 |
Jun is the wettest month (4.94 in, 3,926 gal off the roof); Jan the driest (0.90 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 Cottage Grove?
Best fit: one 55-gallon barrel, which delivers about 422 gallons to the garden in a normal year (79.3% 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 Cottage Grove's roof water will pass straight through it.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 422 | 25,064 |
| 110 gal | 422 | 25,064 |
| 165 gal | 422 | 25,064 |
| 275 gal | 422 | 25,064 |
| 550 gal | 422 | 25,064 |
| 1,000 gal | 422 | 25,064 |
| 1,500 gal | 422 | 25,064 |
| 2,500 gal | 422 | 25,064 |
| 5,000 gal | 422 | 25,064 |
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