Mackay
Dam in Custer County, Idaho · Big Lost River Sinks · forms Mackay Reservoir
Height
75 ft
23 m (NID height)
Length
1,430 ft
436 m
Completed
1918
Mackay Reservoir today
22.19 ft
7 days ▲ 2.83 ft
Normal storage
45,000 acre-ft
Below normal for the date
Reservoir level measured Oct 23, 2026, 10:45 AM MDT. Full level page →
Facts
- Purposes
- Other
- Owner
- Private
- Maximum storage
- 45,000 acre-ft
- Surface area
- 1,392 acres
- Hydraulic height
- 67 ft
- Drainage area
- 788 sq mi
- Spillway
- Uncontrolled, 73 ft wide
- Army Corps district
- Walla Walla District
- NID ID
- ID00181
Facts from the U.S. Army Corps of Engineers National Inventory of Dams, record updated Oct 6, 2026. Search NID ID ID00181 at nid.sec.usace.army.mil. Project website.