| Geist Reservoir | |
|---|---|
 | |
  Geist Reservoir  Geist Reservoir | |
| Location | Indianapolis / Fishers, Indiana |
| Coordinates | 39°55′37″N 85°57′36″W / 39.927°N 85.96°W |
| Type | Reservoir |
| Primary inflows | Fall Creek |
| Primary outflows | Fall Creek |
| Basin countries | United States |
| Surface area | 1,890 acres (7.6 km2) |
| Water volume | 6,100,000,000 US gal (0.023 km3) |
Geist Reservoir is a reservoir in the northeastern part of metropolitan Indianapolis, Indiana, United States. It was constructed in 1943 by damming Fall Creek to provide water for Indianapolis. Upon completion, Geist Reservoir was the second-largest man-made lake in Indiana, providing approximately 6,900,000,000 US gallons (2.6×1010 L; 5.7×109 imp gal) of water. The reservoir is located primarily in the northeast corner of Indianapolis and the southeast corner of Fishers, but small parts reach into the nearby towns of Lawrence, Fortville, and McCordsville.