Saginaw, MI rainwater: 27,007 gallons off a roof

Saginaw, MI: gallons off the roof each year

27,007gallons a year

That is a 1,500 sq ft asphalt roof under Saginaw, MI's normal 34.0 inches of rain, about 795 gallons for every inch that falls.

In Saginaw, MI 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 Saginaw #3 station (0.4 mi away). Saginaw, MI ranks 58th wettest of the 90 cities covered in Michigan.

Month by month in Saginaw

Month	Rain (in)	Off the roof (gal)	Garden shortfall (gal)
Jan	2.25	1,788
Feb	1.94	1,542
Mar	2.00	1,590
Apr	3.61	2,869	92
May	3.59	2,853	95
Jun	3.48	2,766	108
Jul	3.36	2,671	123
Aug	3.49	2,774	107
Sep	2.68	2,130	208
Oct	2.93	2,329	177
Nov	2.62	2,082
Dec	2.03	1,613

Apr is the wettest month (3.61 in, 2,869 gal off the roof); Feb the driest (1.94 in). Garden shortfall is what a 200 sq ft vegetable bed needs beyond the rain that lands on it, April to October.

Which tank size is worth it in Saginaw

Best fit: one 55-gallon barrel, which delivers about 710 gallons to the garden in a normal year (77.9% 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 Saginaw's roof water will pass straight through it.

Tank	Water used (gal/yr)	Spills over (gal/yr)
55 gal	710	25,157
110 gal	710	25,157
165 gal	710	25,157
275 gal	710	25,157
550 gal	710	25,157
1,000 gal	710	25,157
1,500 gal	710	25,157
2,500 gal	710	25,157
5,000 gal	710	25,157

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 Michigan?

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