Reservoir · Idaho · United States · BOR RISE
Arrowrock Reservoir and Dam (ARK)
33.2% full
Capacity
335.78 hm³
Volume stored
111 hm³
Coordinates
43.595°N, 115.923°W
Last updated
2026-07-28
Current fill
33.2%vs 7 days ago
-1.0%losing
vs 1 year ago
-52.9%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: 2026-07-28.
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 (ARK)
As of July 28, 2026, Arrowrock Reservoir and Dam (ARK) is filled to 33.2% of its total capacity, holding roughly 111 hm³ of water out of a maximum 336 hm³. At this level the reservoir is low.
Over the most recent week on record the fill level has held broadly steady (-1.0 pts), and it is 52.9 points below its level on the same date a year earlier.
Across the readings we hold for Arrowrock Reservoir and Dam (ARK) — 2189 data points between July 31, 2021 and July 28, 2026 — the level has ranged from a low of 15.3% (July 31, 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
- 33.2%
- Water stored
- 111 hm³
- Total capacity
- 336 hm³
- 7-day change
- ▼ 1.0 pts
- Year-on-year
- ▼ 52.9 pts
- Primary use
- Multipurpose
- River basin
- Idaho
- Operator
- BOR
- Coordinates
- 43.595°N, 115.923°W
- Last updated
- July 28, 2026
Recent readings
| Date | Fill level | Volume (hm³) |
|---|---|---|
| 28 Jul 2026 | 33.2% | 111 |
| 27 Jul 2026 | 34.2% | 115 |
| 26 Jul 2026 | 35.2% | 118 |
| 25 Jul 2026 | 36.3% | 122 |
| 24 Jul 2026 | 37.4% | 126 |
| 23 Jul 2026 | 38.6% | 130 |
| 22 Jul 2026 | 39.7% | 133 |
| 21 Jul 2026 | 40.7% | 137 |
| 20 Jul 2026 | 41.6% | 140 |
| 19 Jul 2026 | 42.6% | 143 |
| 18 Jul 2026 | 43.6% | 146 |
| 17 Jul 2026 | 44.5% | 149 |
Frequently asked questions
What is the current water level of Arrowrock Reservoir and Dam (ARK)?
As of July 28, 2026, Arrowrock Reservoir and Dam (ARK) is at 33.2% of its capacity, holding approximately 111 hm³ of water, according to BOR RISE (US Bureau of Reclamation) data.
Is Arrowrock Reservoir and Dam (ARK) reservoir full?
No. As of July 28, 2026, Arrowrock Reservoir and Dam (ARK) is low at 33.2% of its capacity, so it is not full.
Is the water level at Arrowrock Reservoir and Dam (ARK) rising or falling?
The level at Arrowrock Reservoir and Dam (ARK) has been broadly stable over the latest week on record (-1.0 points).
How much water can Arrowrock Reservoir and Dam (ARK) hold?
Arrowrock Reservoir and Dam (ARK) has a total capacity of 336 hm³.
Where is Arrowrock Reservoir and Dam (ARK) reservoir located?
Arrowrock Reservoir and Dam (ARK) is located in Idaho, United States, within the Idaho basin (coordinates 43.595°N, 115.923°W).
What is Arrowrock Reservoir and Dam (ARK) used for?
Arrowrock Reservoir and Dam (ARK) is used primarily for multiple purposes, and is managed by BOR.