Blackfoot, ID rainwater: 9,577 gallons off a roof
Blackfoot, ID: gallons off the roof each year
9,577gallons a year
That is a 1,500 sq ft asphalt roof under Blackfoot, ID's normal 12.1 inches of rain, about 795 gallons for every inch that falls.
Blackfoot, ID has gaps between storms long enough to drain a single barrel. Around 165 gallons of storage catches most of what is worth catching.
Rainfall: NOAA 1991-2020 climate normals, the Blackfoot Fire Dept station (0.2 mi away). Blackfoot, ID ranks 20th wettest of the 26 cities covered in Idaho.
Month by month in Blackfoot
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 0.99 | 787 | |
| Feb | 0.73 | 580 | |
| Mar | 1.10 | 874 | |
| Apr | 1.40 | 1,113 | 368 |
| May | 1.75 | 1,391 | 324 |
| Jun | 1.03 | 819 | 414 |
| Jul | 0.50 | 397 | 480 |
| Aug | 0.60 | 477 | 468 |
| Sep | 0.97 | 771 | 421 |
| Oct | 1.12 | 890 | 403 |
| Nov | 0.75 | 596 | |
| Dec | 1.11 | 882 |
May is the wettest month (1.75 in, 1,391 gal off the roof); Jul the driest (0.50 in). Garden shortfall is what a 200 sq ft vegetable bed needs beyond the rain that lands on it, April to October.
Which tank size is worth it in Blackfoot
Best fit: 3 linked 55-gallon barrels, which delivers about 2,404 gallons to the garden in a normal year (83.5% of its need).
If you buy one, link barrels with a short hose at the base so they fill and drain together, and check the overflow points away from the house.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 1,236 | 7,771 |
| 110 gal | 2,045 | 6,963 |
| 165 gal | 2,404 | 6,603 |
| 275 gal | 2,593 | 6,415 |
| 550 gal | 2,593 | 6,415 |
| 1,000 gal | 2,593 | 6,415 |
| 1,500 gal | 2,593 | 6,415 |
| 2,500 gal | 2,593 | 6,415 |
| 5,000 gal | 2,593 | 6,415 |
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 Idaho?
Allowed through a legal clarification made by the Office of the Attorney General
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