Reservoir · Wyoming · United States · BOR RISE
Guernsey Reservoir
Guernsey Reservoir Dam and Powerplant
15.0% full
Capacity
56.26 hm³
Volume stored
8 hm³
Vs month average
120% of normal
Coordinates
42.289°N, 104.763°W
Last updated
2026-10-27
Current fill
15.0%vs 7 days ago
+0.7 ppgaining
vs 1 year ago
-4.8 ppyear-over-year
7-day trend
→stable
Drought context
Storage vs October average
120%of normal
15.0% full on 2026-10-27, against an average of 12.5% for October across 6 years of readings (+2.5 points).
Drought Monitor at this site · 20 October 2026
D1moderate drought
The ground at Guernsey Reservoir's coordinates falls inside the D1 area of the weekly U.S. Drought Monitor map. That describes local conditions — rainfall, soil moisture, streamflow — not the reservoir's storage. Wyoming 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. 42.289°N, 104.763°W · Open in Google Maps
About Guernsey Reservoir
As of October 27, 2026, Guernsey Reservoir is filled to 15.0% of its total capacity, holding 8.46 hm³ of water out of a maximum 56.26 hm³. At this level the reservoir is critically low.
Over the most recent week on record the fill level has held broadly steady (+0.7 pp), and it is 4.8 points below its level on the same date a year earlier.
Across the readings we hold for Guernsey Reservoir — 1944 data points between October 29, 2021 and October 27, 2026 — the level has ranged from a low of 1.2% (October 29, 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 is at 42.289°N, 104.763°W.
Key facts
- Current fill level
- 15.0% of total capacity
- Water stored
- 8.46 hm³
- Total capacity
- 56.26 hm³
- 7-day change
- ▲ 0.7 pp
- Year-on-year
- ▼ 4.8 pp
- Primary use
- Multipurpose
- Operator
- BOR
- Coordinates
- 42.289°N, 104.763°W
- Last updated
- October 27, 2026
Recent readings
| Date | Fill level | Volume (hm³) |
|---|---|---|
| 27 Oct 2026 | 15.0% | 8.46 |
| 26 Oct 2026 | 14.9% | 8.38 |
| 25 Oct 2026 | 14.8% | 8.33 |
| 24 Oct 2026 | 14.7% | 8.28 |
| 23 Oct 2026 | 14.6% | 8.23 |
| 22 Oct 2026 | 14.5% | 8.16 |
| 21 Oct 2026 | 14.4% | 8.1 |
| 20 Oct 2026 | 14.3% | 8.03 |
| 19 Oct 2026 | 14.1% | 7.94 |
| 18 Oct 2026 | 14.0% | 7.89 |
| 17 Oct 2026 | 13.9% | 7.8 |
| 16 Oct 2026 | 13.7% | 7.71 |