Reservoir · Wyoming · United States · BOR RISE
Grassy Lake and Grassy Lake Dam (GRS)
96.8% full
Capacity
19.08 hm³
Volume stored
19 hm³
Coordinates
44.130°N, 110.819°W
Last updated
2026-06-11
Current fill
96.8%vs 7 days ago
0.0%stable
vs 1 year ago
+5.8%year-over-year
7-day trend
→stable
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: 2026-06-11.
Catchment Weather
Past 30 days + 14-day forecast · Open-Meteo
Satellite imagery: Esri, Maxar, Earthstar Geographics. Map: Esri, HERE, Garmin, © OpenStreetMap contributors. 44.130, -110.819 · Open in Google Maps
About Grassy Lake and Grassy Lake Dam (GRS)
As of June 11, 2026, Grassy Lake and Grassy Lake Dam (GRS) is filled to 96.8% of its total capacity, holding roughly 19 hm³ of water out of a maximum 19 hm³. At this level the reservoir is high.
Over the most recent week on record the fill level has held broadly steady (+0.0 pts), and it is 5.8 points above its level on the same date a year earlier.
Across the readings we hold for Grassy Lake and Grassy Lake Dam (GRS) — 2192 data points between June 13, 2021 and June 11, 2026 — the level has ranged from a low of 55.7% (July 28, 2021) to a high of 99.8% (June 7, 2022). On average the reservoir is fullest around June and at its lowest around August.
It is operated by BOR primarily for multiple purposes. It lies within the Wyoming basin at 44.130°N, 110.819°W.
Key facts
- Current fill level
- 96.8%
- Water stored
- 19 hm³
- Total capacity
- 19 hm³
- 7-day change
- No change
- Year-on-year
- ▲ 5.8 pts
- Primary use
- Multipurpose
- River basin
- Wyoming
- Operator
- BOR
- Coordinates
- 44.130°N, 110.819°W
- Last updated
- June 11, 2026
Recent readings
| Date | Fill level | Volume (hm³) |
|---|---|---|
| 11 Jun 2026 | 96.8% | 18 |
| 10 Jun 2026 | 96.8% | 18 |
| 9 Jun 2026 | 96.8% | 18 |
| 8 Jun 2026 | 96.8% | 18 |
| 7 Jun 2026 | 96.8% | 18 |
| 6 Jun 2026 | 96.8% | 18 |
| 5 Jun 2026 | 96.8% | 18 |
| 4 Jun 2026 | 96.8% | 18 |
| 3 Jun 2026 | 96.8% | 18 |
| 2 Jun 2026 | 96.7% | 18 |
| 1 Jun 2026 | 96.6% | 18 |
| 31 May 2026 | 96.5% | 18 |
Frequently asked questions
What is the current water level of Grassy Lake and Grassy Lake Dam (GRS)?
As of June 11, 2026, Grassy Lake and Grassy Lake Dam (GRS) is at 96.8% of its capacity, holding approximately 19 hm³ of water, according to BOR RISE (US Bureau of Reclamation) data.
Is Grassy Lake and Grassy Lake Dam (GRS) reservoir full?
Grassy Lake and Grassy Lake Dam (GRS) is essentially full, sitting at 96.8% of capacity as of June 11, 2026.
Is the water level at Grassy Lake and Grassy Lake Dam (GRS) rising or falling?
The level at Grassy Lake and Grassy Lake Dam (GRS) has been broadly stable over the latest week on record (0.0 points).
How much water can Grassy Lake and Grassy Lake Dam (GRS) hold?
Grassy Lake and Grassy Lake Dam (GRS) has a total capacity of 19 hm³.
Where is Grassy Lake and Grassy Lake Dam (GRS) reservoir located?
Grassy Lake and Grassy Lake Dam (GRS) is located in Wyoming, United States, within the Wyoming basin (coordinates 44.130°N, 110.819°W).
What is Grassy Lake and Grassy Lake Dam (GRS) used for?
Grassy Lake and Grassy Lake Dam (GRS) is used primarily for multiple purposes, and is managed by BOR.