Mountain Home, ID rainwater: 8,528 gallons off a roof
Mountain Home, ID: gallons off the roof each year
8,528gallons a year
That is a 1,500 sq ft asphalt roof under Mountain Home, ID's normal 10.7 inches of rain, about 795 gallons for every inch that falls.
Mountain Home, ID's rain arrives in a wet season and stops, so storage is what matters. It takes a cistern of 1,000 gallons to carry spring rain into the dry months.
Rainfall: NOAA 1991-2020 climate normals, the Hammett 2.0 W station (17.2 mi away). Mountain Home, ID ranks 23rd wettest of the 26 cities covered in Idaho.
Month by month in Mountain Home
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 1.24 | 986 | |
| Feb | 0.78 | 620 | |
| Mar | 0.76 | 604 | |
| Apr | 0.98 | 779 | 420 |
| May | 1.35 | 1,073 | 374 |
| Jun | 0.85 | 676 | 436 |
| Jul | 0.27 | 215 | 509 |
| Aug | 0.22 | 175 | 515 |
| Sep | 0.40 | 318 | 492 |
| Oct | 0.91 | 723 | 429 |
| Nov | 1.35 | 1,073 | |
| Dec | 1.62 | 1,288 |
Dec is the wettest month (1.62 in, 1,288 gal off the roof); Aug the driest (0.22 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 Mountain Home
Best fit: a 1,000-gallon cistern, which delivers about 2,777 gallons to the garden in a normal year (87.5% of its need).
If you set one up, ask about a rebate first: cistern-sized storage costs real money, and a buried or tall tank may need a permit. Place it where a full tank (about 8.3 lb a gallon) sits on firm, level ground.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 770 | 7,124 |
| 110 gal | 1,392 | 6,501 |
| 165 gal | 1,722 | 6,171 |
| 275 gal | 2,024 | 5,870 |
| 550 gal | 2,327 | 5,567 |
| 1,000 gal | 2,777 | 5,117 |
| 1,500 gal | 2,995 | 4,898 |
| 2,500 gal | 2,995 | 4,898 |
| 5,000 gal | 2,995 | 4,796 |
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