Lakes / Colorado / Larimer County / Mariano Reservoir
Mariano Reservoir, Colorado
376 acres
Surface Area
Where It Sits, and How Deep It Goes
Locator - Colorado
40.39 degrees N, 105.14 degrees W - Larimer County. State and county outlines drawn from Census boundary data; the lake marker is placed by its USGS National Hydrography Dataset coordinates, not by eye. Schematic - not a survey map.
How Mariano Reservoir Stacks Up
- Larger than 87% of the 778 lakes counted in Colorado.
- About 27 miles from Boulder, as the crow flies.
Lakes Nearby
| Lake | County | Distance | Surface Area |
|---|---|---|---|
| George Rist Reservoir | Larimer | 0.6 mi | 42 acres |
| Lon Hagler Reservoir | Larimer | 1.5 mi | 150 acres |
| Rist Benson Reservoir | Larimer | 2.2 mi | 51 acres |
| South Side Reservoir | Larimer | 2.2 mi | 64 acres |
| Ryan Gulch Reservoir | Larimer | 2.2 mi | 87 acres |
| Lake Loveland | Larimer | 3.4 mi | 443 acres |
Straight-line distance between lake centers.
Facts and Figures
Questions About Mariano Reservoir
How Big Is Mariano Reservoir?
Mariano Reservoir covers 376 acres in Larimer County, Colorado.
What Is the Largest Lake in Larimer County?
Horsetooth Reservoir is the largest lake in Larimer County, at 1,817 acres.
Largest Lakes in Colorado
| # | Lake | County | Surface Area | Max Depth |
|---|---|---|---|---|
| 1 | John Martin Reservoir | Bent | 11,686 acres | - |
| 2 | Blue Mesa Reservoir | Gunnison | 8,944 acres | - |
| 3 | Lake Granby | Grand | 7,075 acres | - |
| 4 | Lake Meredith | Crowley | 5,539 acres | - |
| 5 | Adobe Creek Reservoir | Bent | 4,770 acres | - |
All 778 Colorado lakes ranked by surface area
Sources: USGS NHD (The National Map NHD MapServer layer 12) named waterbodies FTYPE 390/436; counties via Census point-in-polygon lake data (ID 120819211). Verified October 30, 2026.