Reservoir · Idaho · United States · BOR RISE
Mann Lake
Mann Lake and Reservoir A Dam
31.7% full
Capacity
4.07 hm³
Volume stored
1 hm³
Coordinates
46.371°N, 116.858°W
Last updated
2026-09-30
Current fill
31.7%vs 7 days ago
+0.5%gaining
vs 1 year ago
+8.1%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: 2026-09-30.
Catchment Weather
Past 30 days + 14-day forecast · Open-Meteo
Satellite imagery: Esri, Maxar, Earthstar Geographics. Map: Esri, HERE, Garmin, © OpenStreetMap contributors. 46.371, -116.858 · Open in Google Maps
About Mann Lake
As of September 30, 2026, Mann Lake is filled to 31.7% of its total capacity, holding roughly 1 hm³ of water out of a maximum 4 hm³. At this level the reservoir is low.
Over the most recent week on record the fill level has held broadly steady (+0.5 pts), and it is 8.1 points above its level on the same date a year earlier.
Across the readings we hold for Mann Lake — 2189 data points between October 2, 2021 and September 30, 2026 — the level has ranged from a low of 23.6% (October 2, 2021) to a high of 73.7% (June 13, 2022). On average the reservoir is fullest around May and at its lowest around January.
It is operated by BOR primarily for multiple purposes. It lies within the Idaho basin at 46.371°N, 116.858°W.
Key facts
- Current fill level
- 31.7%
- Water stored
- 1 hm³
- Total capacity
- 4 hm³
- 7-day change
- ▲ 0.5 pts
- Year-on-year
- ▲ 8.1 pts
- Primary use
- Multipurpose
- River basin
- Idaho
- Operator
- BOR
- Coordinates
- 46.371°N, 116.858°W
- Last updated
- September 30, 2026
Recent readings
| Date | Fill level | Volume (hm³) |
|---|---|---|
| 30 Sep 2026 | 31.7% | 1 |
| 29 Sep 2026 | 31.9% | 1 |
| 28 Sep 2026 | 31.9% | 1 |
| 27 Sep 2026 | 31.7% | 1 |
| 26 Sep 2026 | 31.7% | 1 |
| 25 Sep 2026 | 31.4% | 1 |
| 24 Sep 2026 | 31.2% | 1 |
| 23 Sep 2026 | 31.2% | 1 |
| 22 Sep 2026 | 31.2% | 1 |
| 21 Sep 2026 | 31.0% | 1 |
| 20 Sep 2026 | 31.0% | 1 |
| 19 Sep 2026 | 31.0% | 1 |