Reservoir · Montana · United States · BOR RISE
Nelson Reservoir
Nelson Reservoir and Nelson Dikes
71.1% full
Capacity
97.72 hm³
Volume stored
69 hm³
Vs month average
98% of normal
Coordinates
48.530°N, 107.519°W
Last updated
2026-10-27
Current fill
71.1%vs 7 days ago
-0.5 pplosing
vs 1 year ago
-3.0 ppyear-over-year
7-day trend
→stable
Drought context
Storage vs October average
98%of normal
71.1% full on 2026-10-27, against an average of 72.8% for October across 6 years of readings (-1.7 points).
Drought Monitor at this site · 20 October 2026
Nonenot in a drought category
Nelson Reservoir's coordinates fall outside every category on 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. 48.530°N, 107.519°W · Open in Google Maps
About Nelson Reservoir
As of October 27, 2026, Nelson Reservoir is filled to 71.1% of its total capacity, holding 69.46 hm³ of water out of a maximum 97.72 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 (-0.5 pp), and it is 3.0 points below its level on the same date a year earlier.
Across the readings we hold for Nelson Reservoir — 1956 data points between October 29, 2021 and October 27, 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 is at 48.530°N, 107.519°W.
Key facts
- Current fill level
- 71.1% of total capacity
- Water stored
- 69.46 hm³
- Total capacity
- 97.72 hm³
- 7-day change
- ▼ 0.5 pp
- Year-on-year
- ▼ 3.0 pp
- Primary use
- Multipurpose
- Operator
- BOR
- Coordinates
- 48.530°N, 107.519°W
- Last updated
- October 27, 2026
Recent readings
| Date | Fill level | Volume (hm³) |
|---|---|---|
| 27 Oct 2026 | 71.1% | 69.46 |
| 26 Oct 2026 | 70.9% | 69.28 |
| 25 Oct 2026 | 71.0% | 69.37 |
| 24 Oct 2026 | 71.2% | 69.55 |
| 23 Oct 2026 | 71.4% | 69.73 |
| 22 Oct 2026 | 71.4% | 69.81 |
| 21 Oct 2026 | 71.5% | 69.9 |
| 20 Oct 2026 | 71.6% | 69.99 |
| 19 Oct 2026 | 71.7% | 70.08 |
| 18 Oct 2026 | 71.8% | 70.13 |
| 17 Oct 2026 | 71.9% | 70.3 |
| 16 Oct 2026 | 72.0% | 70.39 |