Reservoir · Wyoming · United States · BOR RISE
Guernsey Reservoir
Guernsey Reservoir Dam and Powerplant
8.6% full
Capacity
56.26 hm³
Volume stored
5 hm³
Coordinates
42.289°N, 104.763°W
Last updated
2026-09-09
Current fill
8.6%vs 7 days ago
+1.7%gaining
vs 1 year ago
-13.0%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. 42.289, -104.763 · Open in Google Maps
About Guernsey Reservoir
As of September 9, 2026, Guernsey Reservoir is filled to 8.6% of its total capacity, holding roughly 5 hm³ of water out of a maximum 56 hm³. At this level the reservoir is critically low.
Over the most recent week on record the fill level has risen by 1.7 percentage points, and it is 13.0 points below its level on the same date a year earlier.
Across the readings we hold for Guernsey Reservoir — 1943 data points between September 12, 2021 and September 9, 2026 — the level has ranged from a low of 1.2% (September 12, 2021) to a high of 84.7% (January 13, 2024). On average the reservoir is fullest around June and at its lowest around October.
It is operated by BOR primarily for multiple purposes. It lies within the Wyoming basin at 42.289°N, 104.763°W.
Key facts
- Current fill level
- 8.6%
- Water stored
- 5 hm³
- Total capacity
- 56 hm³
- 7-day change
- ▲ 1.7 pts
- Year-on-year
- ▼ 13.0 pts
- Primary use
- Multipurpose
- River basin
- Wyoming
- Operator
- BOR
- Coordinates
- 42.289°N, 104.763°W
- Last updated
- September 9, 2026
Recent readings
| Date | Fill level | Volume (hm³) |
|---|---|---|
| 9 Sep 2026 | 8.6% | 5 |
| 8 Sep 2026 | 8.5% | 5 |
| 7 Sep 2026 | 8.2% | 5 |
| 6 Sep 2026 | 8.0% | 4 |
| 5 Sep 2026 | 7.7% | 4 |
| 4 Sep 2026 | 7.5% | 4 |
| 3 Sep 2026 | 7.2% | 4 |
| 2 Sep 2026 | 6.9% | 4 |
| 1 Sep 2026 | 6.5% | 4 |
| 31 Aug 2026 | 5.3% | 3 |
| 30 Aug 2026 | 6.2% | 3 |
| 29 Aug 2026 | 9.5% | 5 |