Reservoir · Utah · United States · BOR RISE
Upper Stillwater Reservoir
Upper Stillwater Reservoir and Dam
42.9% full
Capacity
40.86 hm³
Volume stored
18 hm³
Coordinates
40.566°N, 110.700°W
Last updated
2026-09-08
Current fill
42.9%vs 7 days ago
-9.1%losing
vs 1 year ago
-17.4%year-over-year
7-day trend
↓falling
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: 2026-09-08.
Catchment Weather
Past 30 days + 14-day forecast · Open-Meteo
Satellite imagery: Esri, Maxar, Earthstar Geographics. Map: Esri, HERE, Garmin, © OpenStreetMap contributors. 40.566, -110.700 · Open in Google Maps
About Upper Stillwater Reservoir
As of September 8, 2026, Upper Stillwater Reservoir is filled to 42.9% of its total capacity, holding roughly 18 hm³ of water out of a maximum 41 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 9.1 percentage points, and it is 17.4 points below its level on the same date a year earlier.
Across the readings we hold for Upper Stillwater Reservoir — 1823 data points between September 12, 2021 and September 8, 2026 — the level has ranged from a low of 4.6% (April 8, 2023) to a high of 95.3% (June 13, 2023). On average the reservoir is fullest around July and at its lowest around April.
It is operated by BOR primarily for multiple purposes. It lies within the Utah basin at 40.566°N, 110.700°W.
Key facts
- Current fill level
- 42.9%
- Water stored
- 18 hm³
- Total capacity
- 41 hm³
- 7-day change
- ▼ 9.1 pts
- Year-on-year
- ▼ 17.4 pts
- Primary use
- Multipurpose
- River basin
- Utah
- Operator
- BOR
- Coordinates
- 40.566°N, 110.700°W
- Last updated
- September 8, 2026
Recent readings
| Date | Fill level | Volume (hm³) |
|---|---|---|
| 8 Sep 2026 | 42.9% | 18 |
| 7 Sep 2026 | 43.8% | 18 |
| 6 Sep 2026 | 45.2% | 18 |
| 5 Sep 2026 | 46.7% | 19 |
| 4 Sep 2026 | 48.2% | 20 |
| 3 Sep 2026 | 49.6% | 20 |
| 2 Sep 2026 | 51.0% | 21 |
| 1 Sep 2026 | 52.0% | 21 |
| 31 Aug 2026 | 52.3% | 21 |
| 30 Aug 2026 | 52.6% | 22 |
| 29 Aug 2026 | 52.6% | 22 |
| 28 Aug 2026 | 52.9% | 22 |