Meridian, ID rainwater: 9,887 gallons off a roof
Meridian, ID: gallons off the roof each year
9,887gallons a year
That is a 1,500 sq ft asphalt roof under Meridian, ID's normal 12.4 inches of rain, about 795 gallons for every inch that falls.
Meridian, 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 Boise 6.1 Sw station (4.8 mi away). Meridian, ID ranks 15th wettest of the 26 cities covered in Idaho.
Month by month in Meridian
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 1.42 | 1,129 | |
| Feb | 1.06 | 842 | |
| Mar | 1.46 | 1,160 | |
| Apr | 1.35 | 1,073 | 374 |
| May | 1.61 | 1,280 | 342 |
| Jun | 0.90 | 715 | 430 |
| Jul | 0.25 | 199 | 511 |
| Aug | 0.23 | 183 | 514 |
| Sep | 0.43 | 342 | 489 |
| Oct | 0.92 | 731 | 428 |
| Nov | 1.19 | 946 | |
| Dec | 1.62 | 1,288 |
Dec is the wettest month (1.62 in, 1,288 gal off the roof); Aug the driest (0.23 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 Meridian
Best fit: a 1,000-gallon cistern, which delivers about 2,819 gallons to the garden in a normal year (91.3% of its need).
Before you buy, 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 | 1,137 | 8,000 |
| 110 gal | 1,729 | 7,409 |
| 165 gal | 2,052 | 7,085 |
| 275 gal | 2,184 | 6,954 |
| 550 gal | 2,459 | 6,679 |
| 1,000 gal | 2,819 | 6,318 |
| 1,500 gal | 2,819 | 6,318 |
| 2,500 gal | 2,819 | 6,318 |
| 5,000 gal | 2,819 | 6,318 |
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