Evans, CO rainwater: 11,906 gallons off a roof
Evans, CO: gallons off the roof each year
11,906gallons a year
That is a 1,500 sq ft asphalt roof under Evans, CO's normal 15.0 inches of rain, about 795 gallons for every inch that falls.
In Evans, CO 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 Greeley 5.2 Sw station (1.5 mi away). Evans, CO ranks 37th wettest of the 53 cities covered in Colorado.
Month by month in Evans
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 0.41 | 326 | |
| Feb | 0.37 | 294 | |
| Mar | 0.98 | 779 | |
| Apr | 1.79 | 1,423 | 319 |
| May | 2.86 | 2,273 | 186 |
| Jun | 1.76 | 1,399 | 323 |
| Jul | 1.72 | 1,367 | 328 |
| Aug | 1.52 | 1,208 | 353 |
| Sep | 1.29 | 1,025 | 382 |
| Oct | 1.18 | 938 | 395 |
| Nov | 0.66 | 525 | |
| Dec | 0.44 | 350 |
May is the wettest month (2.86 in, 2,273 gal off the roof); Feb the driest (0.37 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 Evans
Best fit: 2 linked 55-gallon barrels, which delivers about 1,985 gallons to the garden in a normal year (86.9% 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 Evans's roof water will pass straight through it.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 1,390 | 9,976 |
| 110 gal | 1,985 | 9,381 |
| 165 gal (over cap) | 2,004 | 9,362 |
| 275 gal (over cap) | 2,004 | 9,362 |
| 550 gal (over cap) | 2,004 | 9,362 |
| 1,000 gal (over cap) | 2,004 | 9,362 |
| 1,500 gal (over cap) | 2,004 | 9,362 |
| 2,500 gal (over cap) | 2,004 | 9,362 |
| 5,000 gal (over cap) | 2,004 | 9,362 |
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 Colorado?
Most households may use rain barrels: a maximum of two rain barrels with a combined storage of 110 gallons or less per household, rooftop runoff only, used outdoors on the same property (HB16-1005). Larger rooftop collection only for qualifying well-permit holders (SB09-080) or pilot projects (HB09-1129).
Checked against the current source on 2026-11-06. Source