Reservoir · Idaho · United States · BOR RISE
Arrowrock Reservoir and Dam
18.4% full
Capacity
335.78 hm³
Volume stored
62 hm³
Coordinates
43.595°N, 115.923°W
Last updated
2026-08-12
Current fill
18.4%vs 7 days ago
-5.4%losing
vs 1 year ago
-7.8%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. 43.595, -115.923 · Open in Google Maps
About Arrowrock Reservoir and Dam
As of August 12, 2026, Arrowrock Reservoir and Dam is filled to 18.4% of its total capacity, holding roughly 62 hm³ of water out of a maximum 336 hm³. At this level the reservoir is critically low.
Over the most recent week on record the fill level has fallen by 5.4 percentage points, and it is 7.8 points below its level on the same date a year earlier.
Across the readings we hold for Arrowrock Reservoir and Dam — 2186 data points between August 15, 2021 and August 12, 2026 — the level has ranged from a low of 16.0% (September 13, 2021) to a high of 98.9% (April 17, 2026). 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 Idaho basin at 43.595°N, 115.923°W.
Key facts
- Current fill level
- 18.4%
- Water stored
- 62 hm³
- Total capacity
- 336 hm³
- 7-day change
- ▼ 5.4 pts
- Year-on-year
- ▼ 7.8 pts
- Primary use
- Multipurpose
- River basin
- Idaho
- Operator
- BOR
- Coordinates
- 43.595°N, 115.923°W
- Last updated
- August 12, 2026
Recent readings
| Date | Fill level | Volume (hm³) |
|---|---|---|
| 12 Aug 2026 | 18.4% | 62 |
| 11 Aug 2026 | 18.6% | 62 |
| 10 Aug 2026 | 19.0% | 64 |
| 9 Aug 2026 | 19.6% | 66 |
| 8 Aug 2026 | 20.6% | 69 |
| 6 Aug 2026 | 22.8% | 77 |
| 5 Aug 2026 | 23.8% | 80 |
| 4 Aug 2026 | 24.9% | 84 |
| 3 Aug 2026 | 26.0% | 87 |
| 2 Aug 2026 | 27.2% | 91 |
| 30 Jul 2026 | 31.0% | 104 |
| 29 Jul 2026 | 32.1% | 108 |
Frequently asked questions
What is the current water level of Arrowrock Reservoir and Dam?
As of August 12, 2026, Arrowrock Reservoir and Dam is at 18.4% of its capacity, holding approximately 62 hm³ of water, according to BOR RISE (US Bureau of Reclamation) data.
Is Arrowrock Reservoir and Dam reservoir full?
No. As of August 12, 2026, Arrowrock Reservoir and Dam is critically low at 18.4% of its capacity, so it is not full.
Is the water level at Arrowrock Reservoir and Dam rising or falling?
The level at Arrowrock Reservoir and Dam is falling — it dropped 5.4 percentage points over the latest week on record.
How much water can Arrowrock Reservoir and Dam hold?
Arrowrock Reservoir and Dam has a total capacity of 336 hm³.
Where is Arrowrock Reservoir and Dam reservoir located?
Arrowrock Reservoir and Dam is located in Idaho, United States, within the Idaho basin (coordinates 43.595°N, 115.923°W).
What is Arrowrock Reservoir and Dam used for?
Arrowrock Reservoir and Dam is used primarily for multiple purposes, and is managed by BOR.