Huron, SD rainwater: 18,535 gallons off a roof

Rainwater from a roof in Huron, SD

18,535gallons a year

That is a 1,500 sq ft asphalt roof under Huron, SD's normal 23.3 inches of rain, about 795 gallons for every inch that falls.

In Huron, SD 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 Huron Rgnl Ap station (2.6 mi away). Huron, SD ranks 8th wettest of the 14 cities covered in South Dakota.

Month by month in Huron

Month	Rain (in)	Off the roof (gal)	Garden shortfall (gal)
Jan	0.58	461
Feb	0.75	596
Mar	1.15	914
Apr	2.52	2,003	228
May	3.15	2,504	150
Jun	3.89	3,092	57
Jul	2.83	2,249	190
Aug	2.59	2,059	219
Sep	2.43	1,931	239
Oct	1.95	1,550	299
Nov	0.82	652
Dec	0.66	525

Jun is the wettest month (3.89 in, 3,092 gal off the roof); Jan the driest (0.58 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 Huron?

Best fit: one 55-gallon barrel, which delivers about 1,120 gallons to the garden in a normal year (81.0% of its need).

Before you buy, a 55-gallon barrel with a downspout diverter is the whole job. Check that the overflow points away from your foundation, because most of Huron's roof water will pass straight through it.

Tank	Water used (gal/yr)	Spills over (gal/yr)
55 gal	1,120	16,695
110 gal	1,160	16,655
165 gal	1,160	16,655
275 gal	1,160	16,655
550 gal	1,160	16,655
1,000 gal	1,160	16,655
1,500 gal	1,160	16,655
2,500 gal	1,160	16,655
5,000 gal	1,160	16,655

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 South Dakota?

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