Reservoir · Montana · United States · BOR RISE
Bighorn Lake
Bighorn Lake Yellowtail Dam and Powerplant
84.8% full
Capacity
1,258.86 hm³
Volume stored
1068 hm³
Vs month average
93% of normal
Coordinates
45.307°N, 107.957°W
Last updated
2026-10-27
Current fill
84.8%vs 7 days ago
+0.1 ppgaining
vs 1 year ago
-6.3 ppyear-over-year
7-day trend
→stable
Drought context
Storage vs October average
93%of normal
84.8% full on 2026-10-27, against an average of 90.8% for October across 6 years of readings (-6.0 points).
Drought Monitor at this site · 20 October 2026
D1moderate drought
The ground at Bighorn Lake's coordinates falls inside the D1 area of the weekly U.S. Drought Monitor map. That describes local conditions — rainfall, soil moisture, streamflow — not the reservoir's storage. Montana drought figures →
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: 2026-10-27.
Catchment Weather
Past 30 days + 14-day forecast · Open-Meteo
Satellite imagery: Esri, Maxar, Earthstar Geographics. Map: Esri, HERE, Garmin, © OpenStreetMap contributors. 45.307°N, 107.957°W · Open in Google Maps
About Bighorn Lake
As of October 27, 2026, Bighorn Lake is filled to 84.8% of its total capacity, holding 1,068 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 (+0.1 pp), and it is 6.3 points below its level on the same date a year earlier.
Across the readings we hold for Bighorn Lake — 2051 data points between October 29, 2021 and October 27, 2026 — the level has ranged from a low of 75.7% (May 8, 2024) to a high of 104.3% (July 16, 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 is at 45.307°N, 107.957°W.
Key facts
- Current fill level
- 84.8% of total capacity
- Water stored
- 1,068 hm³
- Total capacity
- 1,259 hm³
- 7-day change
- ▲ 0.1 pp
- Year-on-year
- ▼ 6.3 pp
- Primary use
- Multipurpose
- Operator
- BOR
- Coordinates
- 45.307°N, 107.957°W
- Last updated
- October 27, 2026
Recent readings
| Date | Fill level | Volume (hm³) |
|---|---|---|
| 27 Oct 2026 | 84.8% | 1,068 |
| 26 Oct 2026 | 84.7% | 1,067 |
| 25 Oct 2026 | 84.7% | 1,067 |
| 24 Oct 2026 | 84.8% | 1,067 |
| 23 Oct 2026 | 84.8% | 1,068 |
| 22 Oct 2026 | 84.8% | 1,068 |
| 21 Oct 2026 | 84.8% | 1,067 |
| 20 Oct 2026 | 84.7% | 1,067 |
| 19 Oct 2026 | 84.7% | 1,067 |
| 18 Oct 2026 | 84.6% | 1,066 |
| 17 Oct 2026 | 84.6% | 1,065 |
| 16 Oct 2026 | 84.4% | 1,063 |