Bowie, MD rainwater: 35,774 gallons off a roof
Rainwater from a roof in Bowie, MD
35,774gallons a year
That is a 1,500 sq ft asphalt roof under Bowie, MD's normal 45.0 inches of rain, about 795 gallons for every inch that falls.
In Bowie, MD 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 Upper Marlboro 3 Nnw station (7.3 mi away). Bowie, MD ranks 14th wettest of the 23 cities covered in Maryland.
Month by month in Bowie
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 2.96 | 2,353 | |
| Feb | 2.66 | 2,114 | |
| Mar | 3.92 | 3,116 | |
| Apr | 3.38 | 2,686 | 121 |
| May | 4.11 | 3,267 | 30 |
| Jun | 4.20 | 3,338 | 19 |
| Jul | 4.22 | 3,354 | 16 |
| Aug | 4.12 | 3,275 | 29 |
| Sep | 4.51 | 3,585 | |
| Oct | 4.13 | 3,283 | 27 |
| Nov | 3.25 | 2,583 | |
| Dec | 3.55 | 2,822 |
Sep is the wettest month (4.51 in, 3,585 gal off the roof); Feb the driest (2.66 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 Bowie
Best fit: one 55-gallon barrel, which delivers about 189 gallons to the garden in a normal year (78.1% of its need).
If you buy one, a 55-gallon barrel with a downspout diverter is the whole job. Check that the overflow points away from your foundation, because most of Bowie's roof water will pass straight through it.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 189 | 34,475 |
| 110 gal | 189 | 34,475 |
| 165 gal | 189 | 34,475 |
| 275 gal | 189 | 34,475 |
| 550 gal | 189 | 34,475 |
| 1,000 gal | 189 | 34,475 |
| 1,500 gal | 189 | 34,475 |
| 2,500 gal | 189 | 34,475 |
| 5,000 gal | 189 | 34,475 |
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 Maryland?
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