Juneau, AK rainwater: 70,372 gallons off a roof
How much rain a roof in Juneau, AK collects
70,372gallons a year
That is a 1,500 sq ft asphalt roof under Juneau, AK's normal 88.5 inches of rain, about 795 gallons for every inch that falls.
Juneau, AK gets enough rain in the growing season that a 200 sq ft garden rarely needs topping up, so a tank here is about saving the occasional dry spell, not a summer of watering.
Rainfall: NOAA 1991-2020 climate normals, the Juneau-Douglas Wwtp station (9.6 mi away). Juneau, AK ranks 1st wettest of the 4 cities covered in Alaska.
Month by month in Juneau
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 8.20 | 6,517 | |
| Feb | 5.05 | 4,014 | |
| Mar | 5.15 | 4,093 | |
| Apr | 5.23 | 4,157 | |
| May | 4.86 | 3,863 | |
| Jun | 5.23 | 4,157 | |
| Jul | 7.68 | 6,104 | |
| Aug | 8.48 | 6,740 | |
| Sep | 11.57 | 9,196 | |
| Oct | 10.13 | 8,051 | |
| Nov | 8.84 | 7,026 | |
| Dec | 8.12 | 6,454 |
Sep is the wettest month (11.57 in, 9,196 gal off the roof); May the driest (4.86 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 Juneau?
Best fit: a 5,000-gallon cistern, which delivers about 0 gallons to the garden in a normal year.
Before you buy, a single 55-gallon barrel is plenty here; spend the money on a first-flush diverter and a screen rather than more storage.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 0 | 68,137 |
| 110 gal | 0 | 68,137 |
| 165 gal | 0 | 68,137 |
| 275 gal | 0 | 68,137 |
| 550 gal | 0 | 68,137 |
| 1,000 gal | 0 | 68,137 |
| 1,500 gal | 0 | 68,137 |
| 2,500 gal | 0 | 68,137 |
| 5,000 gal | 0 | 68,137 |
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 Alaska?
No rainwater harvesting regulations
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