Granby Dam

Granby Dam, Spillway and Tunnel Outlet Works are located in a steep, narrow canyon composed of Precambrian crystalline rocks.  Several small faults and rock with varying degrees of hardness and weathering were encountered in the cutoff trench, spillway and tunnel excavations.  Fractured, loose and weathered rocks were removed from foundation areas during construction.  The dam outside the limits of the cutoff trench rests on granular alluvium up to 65 feet in thickness; the soil types are unknown.  Dikes No. 1, 2 and 4 are founded on siltstone of the North Park Formation.  Two faults bound the area of the dikes.  One passes from the left abutment of Dike No. 2 down the valley southwestward approximately parallel to the axis of DIKE No. 1.  The other trends due north and passes under the West End of Dike No. 1.  These faults have broken the siltstone

RegionFacilities in Great Plains | Great Plains Home Page
ProjectColorado-Big Thompson
Dam Type
ReservoirLake Granby
WatercourseColorado River
Original Construction1941-1950
Modified Construction
National ID NumberCO01656
Hydrologic Unit Code

Structural Height298.00 ft
Hydraulic Height (Normal Operating Depth at Dam)223.0 ft
Top Parapet (Elevation)
Spillway Crest Elevation8260.00 ft
Crest Elevation8290.00 ft
Crest Length861.00 ft
Crest Width
Base Width
Volume of Dam Construction Materials
Streambed at Dam Axis8059.00 ft
Top of Exclusive Flood Control Pool (Elevation)
Top of Joint Use Pool (Elevation)8280.00 ft
Top of Active Conservation Pool (Elevation)8279.50 ft
Top of Inactive Conservation Pool (Elevation)8186.00 ft
Top of Dead Storage Pool (Elevation)8174.63 ft

Hydraulics & Hydrology
Total Water Storage at Elevation
Maximum Water Surface Elevation
Normal Water Surface Elevation8279.5 ft
Spillway Type
Auxiliary SpillwayNo
Spillway Capacity at Elevation11500 cfs at 8280.0 ft
Auxiliary Spillway Capacity at Elevation
Uncontrolled Spillway Capacity at Elevation
Outlet Works Capacity at Elevation435 cfs at 8280.0 ft
Diversion Capacity at Elevation
Drainage Area311.0 sq mi
Hydrometeorological Report (HMR)HMR 49
Probable Maximum Flood (PMF) Report

Contact Information
TitleArea Office Manager
OrganizationEastern Colorado Area Office
Address11056 W. County Rd 18E
CityLoveland, CO 80537-9711
Phone (Fax)970 663-3212
Phone (Office)970 667-4410
OrganizationNorthern Colorado Water Conservancy District
AddressPO Box 679
CityLoveland, CO 80539
Phone (Office)970 667-2437

Last updated: Mar 29, 2013