Reservoir · Montana · United States · BOR RISE
Bighorn Lake
Bighorn Lake Yellowtail Dam and Powerplant
82.3% full
Capacity
1,258.86 hm³
Volume stored
1036 hm³
Coordinates
45.307°N, 107.957°W
Last updated
2026-09-09
Current fill
82.3%vs 7 days ago
0.0%stable
vs 1 year ago
-2.4%year-over-year
7-day trend
→stable
Data source: BOR RISE — US Bureau of Reclamation — daily reservoir storage volume. Capacity is the design (normal full-pool) capacity from the US National Inventory of Dams (NID); fill % = current volume ÷ design capacity. Last reading: 2026-09-09.
Catchment Weather
Past 30 days + 14-day forecast · Open-Meteo
Satellite imagery: Esri, Maxar, Earthstar Geographics. Map: Esri, HERE, Garmin, © OpenStreetMap contributors. 45.307, -107.957 · Open in Google Maps
About Bighorn Lake
As of September 9, 2026, Bighorn Lake is filled to 82.3% of its total capacity, holding roughly 1,036 hm³ of water out of a maximum 1,259 hm³. At this level the reservoir is high.
Over the most recent week on record the fill level has held broadly steady (+0.0 pts), and it is 2.4 points below its level on the same date a year earlier.
Across the readings we hold for Bighorn Lake — 2072 data points between September 12, 2021 and September 9, 2026 — the level has ranged from a low of 75.7% (May 8, 2024) to a high of 105.0% (June 24, 2023). On average the reservoir is fullest around July and at its lowest around April.
It is operated by BOR primarily for multiple purposes. It lies within the Montana basin at 45.307°N, 107.957°W.
Key facts
- Current fill level
- 82.3%
- Water stored
- 1,036 hm³
- Total capacity
- 1,259 hm³
- 7-day change
- No change
- Year-on-year
- ▼ 2.4 pts
- Primary use
- Multipurpose
- River basin
- Montana
- Operator
- BOR
- Coordinates
- 45.307°N, 107.957°W
- Last updated
- September 9, 2026
Recent readings
| Date | Fill level | Volume (hm³) |
|---|---|---|
| 9 Sep 2026 | 82.3% | 1,036 |
| 8 Sep 2026 | 82.3% | 1,037 |
| 7 Sep 2026 | 82.3% | 1,037 |
| 6 Sep 2026 | 82.3% | 1,036 |
| 5 Sep 2026 | 82.3% | 1,036 |
| 4 Sep 2026 | 82.3% | 1,037 |
| 3 Sep 2026 | 82.3% | 1,037 |
| 2 Sep 2026 | 82.3% | 1,036 |
| 1 Sep 2026 | 82.3% | 1,036 |
| 31 Aug 2026 | 82.2% | 1,035 |
| 30 Aug 2026 | 82.1% | 1,034 |
| 29 Aug 2026 | 82.1% | 1,033 |