Reservoir · Montana · United States · BOR RISE
Nelson Reservoir
Nelson Reservoir and Nelson Dikes
72.7% full
Capacity
97.72 hm³
Volume stored
71 hm³
Coordinates
48.530°N, 107.519°W
Last updated
2026-10-08
Current fill
72.7%vs 7 days ago
-0.8%losing
vs 1 year ago
-3.4%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: 2026-10-08.
Catchment Weather
Past 30 days + 14-day forecast · Open-Meteo
Satellite imagery: Esri, Maxar, Earthstar Geographics. Map: Esri, HERE, Garmin, © OpenStreetMap contributors. 48.530, -107.519 · Open in Google Maps
About Nelson Reservoir
As of October 8, 2026, Nelson Reservoir is filled to 72.7% of its total capacity, holding roughly 71 hm³ of water out of a maximum 98 hm³. At this level the reservoir is within its normal operating range.
Over the most recent week on record the fill level has held broadly steady (-0.8 pts), and it is 3.4 points below its level on the same date a year earlier.
Across the readings we hold for Nelson Reservoir — 1956 data points between October 10, 2021 and October 8, 2026 — the level has ranged from a low of 43.7% (August 21, 2022) to a high of 99.0% (May 6, 2024). On average the reservoir is fullest around May and at its lowest around February.
It is operated by BOR primarily for multiple purposes. It lies within the Montana basin at 48.530°N, 107.519°W.
Key facts
- Current fill level
- 72.7%
- Water stored
- 71 hm³
- Total capacity
- 98 hm³
- 7-day change
- ▼ 0.8 pts
- Year-on-year
- ▼ 3.4 pts
- Primary use
- Multipurpose
- River basin
- Montana
- Operator
- BOR
- Coordinates
- 48.530°N, 107.519°W
- Last updated
- October 8, 2026
Recent readings
| Date | Fill level | Volume (hm³) |
|---|---|---|
| 8 Oct 2026 | 72.7% | 71 |
| 7 Oct 2026 | 72.8% | 71 |
| 6 Oct 2026 | 72.9% | 71 |
| 5 Oct 2026 | 73.0% | 71 |
| 4 Oct 2026 | 73.1% | 71 |
| 3 Oct 2026 | 73.2% | 72 |
| 2 Oct 2026 | 73.4% | 72 |
| 1 Oct 2026 | 73.5% | 72 |
| 30 Sep 2026 | 73.6% | 72 |
| 29 Sep 2026 | 73.8% | 72 |
| 28 Sep 2026 | 73.9% | 72 |
| 27 Sep 2026 | 74.0% | 72 |