Reservoir · Washington · United States · BOR RISE
Potholes Reservoir and O'Sullivan Dam
18.4% full
Capacity
631.17 hm³
Volume stored
116 hm³
Coordinates
46.983°N, 119.276°W
Last updated
2026-08-12
Current fill
18.4%vs 7 days ago
-3.8%losing
vs 1 year ago
+3.6%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: 2026-08-12.
Catchment Weather
Past 30 days + 14-day forecast · Open-Meteo
Satellite imagery: Esri, Maxar, Earthstar Geographics. Map: Esri, HERE, Garmin, © OpenStreetMap contributors. 46.983, -119.276 · Open in Google Maps
About Potholes Reservoir and O'Sullivan Dam
As of August 12, 2026, Potholes Reservoir and O'Sullivan Dam is filled to 18.4% of its total capacity, holding roughly 116 hm³ of water out of a maximum 631 hm³. At this level the reservoir is critically low.
Over the most recent week on record the fill level has fallen by 3.8 percentage points, and it is 3.6 points above its level on the same date a year earlier.
Across the readings we hold for Potholes Reservoir and O'Sullivan Dam — 2147 data points between August 15, 2021 and August 12, 2026 — the level has ranged from a low of 4.9% (September 3, 2025) to a high of 77.3% (May 17, 2026). On average the reservoir is fullest around May and at its lowest around September.
It is operated by BOR primarily for multiple purposes. It lies within the Washington basin at 46.983°N, 119.276°W.
Key facts
- Current fill level
- 18.4%
- Water stored
- 116 hm³
- Total capacity
- 631 hm³
- 7-day change
- ▼ 3.8 pts
- Year-on-year
- ▲ 3.6 pts
- Primary use
- Multipurpose
- River basin
- Washington
- Operator
- BOR
- Coordinates
- 46.983°N, 119.276°W
- Last updated
- August 12, 2026
Recent readings
| Date | Fill level | Volume (hm³) |
|---|---|---|
| 12 Aug 2026 | 18.4% | 116 |
| 11 Aug 2026 | 19.0% | 120 |
| 10 Aug 2026 | 19.6% | 124 |
| 9 Aug 2026 | 20.2% | 128 |
| 8 Aug 2026 | 20.8% | 131 |
| 7 Aug 2026 | 21.1% | 133 |
| 6 Aug 2026 | 21.7% | 137 |
| 5 Aug 2026 | 22.2% | 140 |
| 4 Aug 2026 | 22.9% | 144 |
| 3 Aug 2026 | 23.7% | 150 |
| 2 Aug 2026 | 24.6% | 155 |
| 1 Aug 2026 | 25.2% | 159 |
Frequently asked questions
What is the current water level of Potholes Reservoir and O'Sullivan Dam?
As of August 12, 2026, Potholes Reservoir and O'Sullivan Dam is at 18.4% of its capacity, holding approximately 116 hm³ of water, according to BOR RISE (US Bureau of Reclamation) data.
Is Potholes Reservoir and O'Sullivan Dam reservoir full?
No. As of August 12, 2026, Potholes Reservoir and O'Sullivan Dam is critically low at 18.4% of its capacity, so it is not full.
Is the water level at Potholes Reservoir and O'Sullivan Dam rising or falling?
The level at Potholes Reservoir and O'Sullivan Dam is falling — it dropped 3.8 percentage points over the latest week on record.
How much water can Potholes Reservoir and O'Sullivan Dam hold?
Potholes Reservoir and O'Sullivan Dam has a total capacity of 631 hm³.
Where is Potholes Reservoir and O'Sullivan Dam reservoir located?
Potholes Reservoir and O'Sullivan Dam is located in Washington, United States, within the Washington basin (coordinates 46.983°N, 119.276°W).
What is Potholes Reservoir and O'Sullivan Dam used for?
Potholes Reservoir and O'Sullivan Dam is used primarily for multiple purposes, and is managed by BOR.