Lakes / Idaho / Franklin County / Foster Reservoir
Foster Reservoir, Idaho
66.22 acres
Surface Area
Where It Sits, and How Deep It Goes
Locator - Idaho
42.13 degrees N, 111.84 degrees W - Franklin 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 Foster Reservoir Stacks Up
- Larger than 44% of the 316 lakes counted in Idaho.
- About 95 miles from Idaho Falls, as the crow flies.
Lakes Nearby
| Lake | County | Distance | Surface Area |
|---|---|---|---|
| Lamont Reservoir | Franklin | 1.7 mi | 88.46 acres |
| Johnson Reservoir | Franklin | 1.9 mi | 43.98 acres |
| Glendale Reservoir | Franklin | 2.2 mi | 207.57 acres |
| Winder Reservoir | Franklin | 4.2 mi | 76.94 acres |
| Condie Reservoir | Franklin | 5.9 mi | 86.24 acres |
| Strongarm Reservoir Number One | Franklin | 7.8 mi | 150.98 acres |
Straight-line distance between lake centers.
Facts and Figures
Questions About Foster Reservoir
How Big Is Foster Reservoir?
Foster Reservoir covers 66.22 acres in Franklin County, Idaho.
What Is the Largest Lake in Franklin County?
Twin Lakes Reservoir is the largest lake in Franklin County, at 439.35 acres.
Largest Lakes in Idaho
| # | Lake | County | Surface Area | Max Depth |
|---|---|---|---|---|
| 1 | Lake Pend Oreille | Bonner | 92,764.44 acres | - |
| 2 | American Falls Reservoir | Power | 55,319.78 acres | - |
| 3 | Coeur d'Alene Lake | Kootenai | 26,891.64 acres | - |
| 4 | Lake Cascade | Valley | 25,043.4 acres | - |
| 5 | Priest Lake | Bonner | 23,425.59 acres | - |
All 316 Idaho lakes ranked by surface area
Sources: USGS National Hydrography Dataset (The National Map) lake data (ID 40846779). Verified October 30, 2026.