Monument, CO rainwater: 15,403 gallons off a roof
Rainwater from a roof in Monument, CO
15,403gallons a year
That is a 1,500 sq ft asphalt roof under Monument, CO's normal 19.4 inches of rain, about 795 gallons for every inch that falls.
In Monument, 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 Monument 1.4 Ne station (0.7 mi away). Monument, CO ranks 6th wettest of the 53 cities covered in Colorado.
Month by month in Monument
| Month | Rain (in) | Off the roof (gal) | Garden shortfall (gal) |
|---|---|---|---|
| Jan | 0.58 | 461 | |
| Feb | 0.73 | 580 | |
| Mar | 1.53 | 1,216 | |
| Apr | 2.44 | 1,939 | 238 |
| May | 2.55 | 2,027 | 224 |
| Jun | 1.71 | 1,359 | 329 |
| Jul | 2.72 | 2,162 | 203 |
| Aug | 3.01 | 2,392 | 167 |
| Sep | 1.60 | 1,272 | 343 |
| Oct | 1.02 | 811 | 415 |
| Nov | 0.80 | 636 | |
| Dec | 0.69 | 548 |
Aug is the wettest month (3.01 in, 2,392 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.
What size rain barrel for Monument
Best fit: 2 linked 55-gallon barrels, which delivers about 1,545 gallons to the garden in a normal year (80.5% 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 Monument's roof water will pass straight through it.
| Tank | Water used (gal/yr) | Spills over (gal/yr) |
|---|---|---|
| 55 gal | 1,379 | 13,124 |
| 110 gal | 1,545 | 12,959 |
| 165 gal (over cap) | 1,566 | 12,938 |
| 275 gal (over cap) | 1,566 | 12,938 |
| 550 gal (over cap) | 1,566 | 12,938 |
| 1,000 gal (over cap) | 1,566 | 12,938 |
| 1,500 gal (over cap) | 1,566 | 12,938 |
| 2,500 gal (over cap) | 1,566 | 12,938 |
| 5,000 gal (over cap) | 1,566 | 12,938 |
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