Atchison, KS rainwater: 28,915 gallons off a roof

Rainwater from a roof in Atchison, KS

28,915gallons a year

That is a 1,500 sq ft asphalt roof under Atchison, KS's normal 36.4 inches of rain, about 795 gallons for every inch that falls.

In Atchison, KS 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 Atchison station (1.6 mi away). Atchison, KS ranks 25th wettest of the 38 cities covered in Kansas.

Month by month in Atchison

Month	Rain (in)	Off the roof (gal)	Garden shortfall (gal)
Jan	0.93	739
Feb	1.20	954
Mar	1.92	1,526
Apr	3.42	2,718	116
May	5.32	4,228
Jun	4.87	3,871
Jul	5.17	4,109
Aug	3.75	2,981	75
Sep	3.48	2,766	108
Oct	3.10	2,464	156
Nov	1.81	1,439
Dec	1.41	1,121

May is the wettest month (5.32 in, 4,228 gal off the roof); Jan the driest (0.93 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 Atchison?

Best fit: one 55-gallon barrel, which delivers about 367 gallons to the garden in a normal year (80.6% 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 Atchison's roof water will pass straight through it.

Tank	Water used (gal/yr)	Spills over (gal/yr)
55 gal	367	27,618
110 gal	367	27,618
165 gal	367	27,618
275 gal	367	27,618
550 gal	367	27,618
1,000 gal	367	27,618
1,500 gal	367	27,618
2,500 gal	367	27,618
5,000 gal	367	27,618

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 Kansas?

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