Reservoir · Montana · United States · BOR RISE
Helena Valley Reservoir
Helena Valley Reservoir and Dam
96.6% full
Capacity
12.89 hm³
Volume stored
13 hm³
Coordinates
46.638°N, 111.882°W
Last updated
2026-09-12
Current fill
96.6%vs 7 days ago
+0.4%gaining
vs 1 year ago
-0.3%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: 2026-09-12.
Catchment Weather
Past 30 days + 14-day forecast · Open-Meteo
Satellite imagery: Esri, Maxar, Earthstar Geographics. Map: Esri, HERE, Garmin, © OpenStreetMap contributors. 46.638, -111.882 · Open in Google Maps
About Helena Valley Reservoir
As of September 12, 2026, Helena Valley Reservoir is filled to 96.6% of its total capacity, holding roughly 13 hm³ of water out of a maximum 13 hm³. At this level the reservoir is high.
Over the most recent week on record the fill level has held broadly steady (+0.4 pts), and it sits close to where it was a year earlier.
Across the readings we hold for Helena Valley Reservoir — 1824 data points between September 15, 2021 and September 12, 2026 — the level has ranged from a low of 60.6% (April 15, 2025) to a high of 99.7% (July 2, 2023). On average the reservoir is fullest around May and at its lowest around March.
It is operated by BOR primarily for multiple purposes. It lies within the Montana basin at 46.638°N, 111.882°W.
Key facts
- Current fill level
- 96.6%
- Water stored
- 13 hm³
- Total capacity
- 13 hm³
- 7-day change
- ▲ 0.4 pts
- Year-on-year
- ▼ 0.3 pts
- Primary use
- Multipurpose
- River basin
- Montana
- Operator
- BOR
- Coordinates
- 46.638°N, 111.882°W
- Last updated
- September 12, 2026
Recent readings
| Date | Fill level | Volume (hm³) |
|---|---|---|
| 12 Sep 2026 | 96.6% | 12 |
| 11 Sep 2026 | 96.6% | 12 |
| 10 Sep 2026 | 96.7% | 12 |
| 9 Sep 2026 | 97.1% | 13 |
| 8 Sep 2026 | 97.5% | 13 |
| 7 Sep 2026 | 97.4% | 13 |
| 6 Sep 2026 | 96.7% | 12 |
| 5 Sep 2026 | 96.2% | 12 |
| 4 Sep 2026 | 95.8% | 12 |
| 3 Sep 2026 | 95.4% | 12 |
| 2 Sep 2026 | 95.0% | 12 |
| 1 Sep 2026 | 94.7% | 12 |