Reservoir · Montana · United States · BOR RISE
Nelson Reservoir
Nelson Reservoir and Nelson Dikes
71.9% full
Capacity
97.72 hm³
Volume stored
70 hm³
Coordinates
48.530°N, 107.519°W
Last updated
2026-09-09
Current fill
71.9%vs 7 days ago
+5.3%gaining
vs 1 year ago
-8.3%year-over-year
7-day trend
↑rising
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. 48.530, -107.519 · Open in Google Maps
About Nelson Reservoir
As of September 9, 2026, Nelson Reservoir is filled to 71.9% of its total capacity, holding roughly 70 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 risen by 5.3 percentage points, and it is 8.3 points below its level on the same date a year earlier.
Across the readings we hold for Nelson Reservoir — 1955 data points between September 12, 2021 and September 9, 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
- 71.9%
- Water stored
- 70 hm³
- Total capacity
- 98 hm³
- 7-day change
- ▲ 5.3 pts
- Year-on-year
- ▼ 8.3 pts
- Primary use
- Multipurpose
- River basin
- Montana
- Operator
- BOR
- Coordinates
- 48.530°N, 107.519°W
- Last updated
- September 9, 2026
Recent readings
| Date | Fill level | Volume (hm³) |
|---|---|---|
| 9 Sep 2026 | 71.9% | 70 |
| 8 Sep 2026 | 71.1% | 70 |
| 7 Sep 2026 | 70.7% | 69 |
| 6 Sep 2026 | 69.3% | 68 |
| 5 Sep 2026 | 68.4% | 67 |
| 4 Sep 2026 | 67.9% | 66 |
| 3 Sep 2026 | 67.2% | 66 |
| 2 Sep 2026 | 66.6% | 65 |
| 1 Sep 2026 | 66.0% | 65 |
| 31 Aug 2026 | 65.7% | 64 |
| 30 Aug 2026 | 65.8% | 64 |
| 29 Aug 2026 | 65.7% | 64 |