Bel Air, MD rainwater: 40,169 gallons off a roof
How much rain a roof in Bel Air, MD collects
40,169gallons a year
That is a 1,500 sq ft asphalt roof under Bel Air, MD's normal 50.5 inches of rain, about 795 gallons for every inch that falls.
In Bel Air, 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 Kingsville 2.5 Nne station (4.5 mi away). Bel Air, MD ranks 1st wettest of the 23 cities covered in Maryland.
Month by month in Bel Air
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 3.50 | 2,782 | |
| Feb | 2.84 | 2,257 | |
| Mar | 4.27 | 3,394 | |
| Apr | 3.62 | 2,877 | 91 |
| May | 4.44 | 3,529 | |
| Jun | 4.64 | 3,688 | |
| Jul | 5.59 | 4,443 | |
| Aug | 4.49 | 3,569 | |
| Sep | 5.27 | 4,189 | |
| Oct | 4.48 | 3,561 | |
| Nov | 3.46 | 2,750 | |
| Dec | 3.94 | 3,132 |
Jul is the wettest month (5.59 in, 4,443 gal off the roof); Feb the driest (2.84 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 Bel Air?
Best fit: one 55-gallon barrel, which delivers about 70 gallons to the garden in a normal year (76.9% of its need).
If you set one up, a 55-gallon barrel with a downspout diverter is the whole job. Check that the overflow points away from your foundation, because most of Bel Air's roof water will pass straight through it.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 70 | 38,810 |
| 110 gal | 70 | 38,810 |
| 165 gal | 70 | 38,810 |
| 275 gal | 70 | 38,810 |
| 550 gal | 70 | 38,810 |
| 1,000 gal | 70 | 38,810 |
| 1,500 gal | 70 | 38,810 |
| 2,500 gal | 70 | 38,810 |
| 5,000 gal | 70 | 38,810 |
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