Located about two miles downstream of Alcova Dam, Gray Reef Dam and Reservoir were constructed as part of the U.S. Bureau of Reclamation (USBR) Glendo Unit, Oregon Trail Division, Pick-Sloan Missouri Basin Program. Gray Reef Reservoir regulates widely fluctuating water releases from Alcova Powerplant. Construction of Gray Reef Dam, which is a rock and earth fill structure, was completed in 1961. More information regarding Gray Reef Dam and Reservoir is available in the following table.
Summary - Storage Capacities of Gray Reef Reservoir
| Permit number |
Reservoir name |
Total capacity |
Outlet capacity |
Spillway capacity |
Hydro-electric |
Power capacity |
Powerplant release |
| SEO tab book (acre-feet) |
(cubic feet per second) |
(cubic feet per second) |
generating plant |
(megawatts) |
SEO tab book (cubic feet per second) |
| P6489R |
Gray Reef Reservoir |
Afterbay to re-regulate Alcova Powerplant |
Unknown |
20,000 |
Unknown |
Unknown |
Unknown |
