GARRISON RESERVOIR AND DAM
OperatingHydro power plant
- Capacity
- 614 MW
- Primary fuel
- Hydro
- County
- Mercer County
- Operator
- USACE-MISSOURI RIVER DISTRICT
- Status
- Operating
- Commissioned
- 1956
- EIA plant ID
- 2815
- Coordinates
- 47.5025, -101.4318
GARRISON RESERVOIR AND DAM, a 614 MW Hydro power plant in Mercer County, North Dakota. Operated by USACE-MISSOURI RIVER DISTRICT, commissioned 1956.
Weather peril exposure
GARRISON RESERVOIR AND DAM is a 614 MW hydro power plant in Mercer County, ND, operated by USACE-MISSOURI RIVER DISTRICT, commissioned in 1956. Mercer County carries critical modeled catastrophe exposure in the FEMA National Risk Index, scoring 4.8 of 5 at the 95th national percentile. Winter weather is the leading peril, rated Relatively Moderate by FEMA at the 98th percentile.
The Bywatts loss layer is calibrated to solar PV hardware, so it is not applied to a hydro plant. The ratings below are the FEMA National Risk Index county hazard ratings for this location.
Mercer County hazard ratings
| Peril | FEMA rating | National percentile | Peril score | Events per year |
|---|---|---|---|---|
| Winter weather | Relatively Moderate | 98th | 4.9 of 5 | 18.4 |
| Hail | Relatively Moderate | 96th | 4.8 of 5 | 2.5 |
| Heat wave | Very Low | 90th | 4.6 of 5 | 1.6 |
| Ice storm | Relatively Moderate | 87th | 4.5 of 5 | 0.64 |
| Wildfire | Very Low | 66th | 3.6 of 5 | <0.01 |
| Strong wind | Relatively Low | 64th | 3.6 of 5 | 1.5 |
| Tornado | Relatively Low | 48th | 2.9 of 5 | 0.32 |
| Riverine flooding | Very Low | 40th | 2.6 of 5 | 0.43 |
| Lightning | Very Low | 36th | 2.5 of 5 | 29.7 |
| Earthquake | Very Low | 6th | 1.3 of 5 | <0.01 |
Perils not assessed in Mercer County
These perils carry no usable National Risk Index figure for this county, so they are excluded from the scoring rather than scored zero. A zero would claim the peril was assessed and found benign.
| Peril | Why it is not scored |
|---|---|
| Hurricane | FEMA rating is "Not Applicable" for this county |
| Coastal flooding | FEMA rating is "Not Applicable" for this county |
Model hail, wind and flood exposure for Mercer County in the weather risk calculator
Ratings are the FEMA National Risk Index county hazard ratings; the peril score is a Bywatts transform of the FEMA national percentile. Full data sources and the solar vulnerability methodology are in the weather risk calculator.
Modeled estimate for screening and negotiation. Built from FEMA National Risk Index county hazard data and a solar vulnerability layer documented above. Not a quote, a binder, or actuarial advice, and not a substitute for a carrier's own model. Hazard data: FEMA National Risk Index December 2025, synced 2026-07-24. Resolution is county level, not site level.