Reservoir · Montana · United States · USACE CWMS
Nelson Reservoir
66.4% full
Capacity
97.72 hm³
Volume stored
65 hm³
Coordinates
48.530°N, 107.519°W
Last updated
2026-08-13
Current fill
66.4%vs 7 days ago
-4.9%losing
vs 1 year ago
-8.3%year-over-year
7-day trend
↓falling
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: 2026-08-13.
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 August 13, 2026, Nelson Reservoir is filled to 66.4% of its total capacity, holding roughly 65 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 fallen by 4.9 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 — 1818 data points between August 15, 2021 and August 13, 2026 — the level has ranged from a low of 43.7% (August 22, 2022) to a high of 99.3% (May 3, 2024). On average the reservoir is fullest around May and at its lowest around February.
It is operated by USACE primarily for multiple purposes. It lies within the Montana basin at 48.530°N, 107.519°W.
Key facts
- Current fill level
- 66.4%
- Water stored
- 65 hm³
- Total capacity
- 98 hm³
- 7-day change
- ▼ 4.9 pts
- Year-on-year
- ▼ 8.3 pts
- Primary use
- Multipurpose
- River basin
- Montana
- Operator
- USACE
- Coordinates
- 48.530°N, 107.519°W
- Last updated
- August 13, 2026
Recent readings
| Date | Fill level | Volume (hm³) |
|---|---|---|
| 13 Aug 2026 | 66.4% | 65 |
| 12 Aug 2026 | 67.0% | 65 |
| 11 Aug 2026 | 67.6% | 66 |
| 10 Aug 2026 | 68.2% | 67 |
| 9 Aug 2026 | 69.0% | 67 |
| 8 Aug 2026 | 69.8% | 68 |
| 7 Aug 2026 | 70.5% | 69 |
| 6 Aug 2026 | 71.3% | 70 |
| 5 Aug 2026 | 72.0% | 70 |
| 4 Aug 2026 | 72.7% | 71 |
| 3 Aug 2026 | 73.5% | 72 |
| 2 Aug 2026 | 74.4% | 73 |
Frequently asked questions
What is the current water level of Nelson Reservoir?
As of August 13, 2026, Nelson Reservoir is at 66.4% of its capacity, holding approximately 65 hm³ of water, according to USACE CWMS (US Army Corps of Engineers) data.
Is Nelson Reservoir reservoir full?
No. As of August 13, 2026, Nelson Reservoir is within its normal operating range at 66.4% of its capacity, so it is not full.
Is the water level at Nelson Reservoir rising or falling?
The level at Nelson Reservoir is falling — it dropped 4.9 percentage points over the latest week on record.
How much water can Nelson Reservoir hold?
Nelson Reservoir has a total capacity of 98 hm³.
Where is Nelson Reservoir reservoir located?
Nelson Reservoir is located in Montana, United States, within the Montana basin (coordinates 48.530°N, 107.519°W).
What is Nelson Reservoir used for?
Nelson Reservoir is used primarily for multiple purposes, and is managed by USACE.