Reservoir · Montana · United States · USACE CWMS
Yellowtail Dam & Reservoir
83.3% full
Capacity
1,258.86 hm³
Volume stored
1049 hm³
Coordinates
45.307°N, 107.958°W
Last updated
2026-10-09
Current fill
83.3%vs 7 days ago
+0.2%gaining
vs 1 year ago
-4.7%year-over-year
7-day trend
→stable
Data source: USACE CWMS — US Army Corps of Engineers — 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: 2026-10-09.
Catchment Weather
Past 30 days + 14-day forecast · Open-Meteo
Satellite imagery: Esri, Maxar, Earthstar Geographics. Map: Esri, HERE, Garmin, © OpenStreetMap contributors. 45.307, -107.958 · Open in Google Maps
About Yellowtail Dam & Reservoir
As of October 9, 2026, Yellowtail Dam & Reservoir is filled to 83.3% of its total capacity, holding roughly 1,049 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 (+0.2 pts), and it is 4.7 points below its level on the same date a year earlier.
Across the readings we hold for Yellowtail Dam & Reservoir — 1822 data points between October 10, 2021 and October 9, 2026 — the level has ranged from a low of 75.7% (May 9, 2024) to a high of 105.0% (June 25, 2023). On average the reservoir is fullest around July and at its lowest around April.
It is operated by USACE primarily for multiple purposes. It lies within the Montana basin at 45.307°N, 107.958°W.
Key facts
- Current fill level
- 83.3%
- Water stored
- 1,049 hm³
- Total capacity
- 1,259 hm³
- 7-day change
- ▲ 0.2 pts
- Year-on-year
- ▼ 4.7 pts
- Primary use
- Multipurpose
- River basin
- Montana
- Operator
- USACE
- Coordinates
- 45.307°N, 107.958°W
- Last updated
- October 9, 2026
Recent readings
| Date | Fill level | Volume (hm³) |
|---|---|---|
| 9 Oct 2026 | 83.3% | 1,049 |
| 8 Oct 2026 | 83.3% | 1,049 |
| 7 Oct 2026 | 83.3% | 1,049 |
| 6 Oct 2026 | 83.3% | 1,049 |
| 5 Oct 2026 | 83.3% | 1,048 |
| 4 Oct 2026 | 83.2% | 1,047 |
| 3 Oct 2026 | 83.2% | 1,047 |
| 2 Oct 2026 | 83.1% | 1,046 |
| 1 Oct 2026 | 83.0% | 1,045 |
| 30 Sep 2026 | 83.0% | 1,045 |
| 29 Sep 2026 | 82.9% | 1,044 |
| 28 Sep 2026 | 82.8% | 1,043 |