Platoro Dam


Platoro Dam is on the Conejos River about 1 mile above the town of Platoro, Colorado. It is an earthfill structure consisting of a main embankment and a dike section, separated by a rock knoll in which the spillway is excavated. The maximum embankment height is 165 feet, and the dam contains 909,884 cubic yards of material. The reservoir formed by the dam has a capacity of 59,570 acre-feet, 6,060 acre-feet of which are for flood control and 53,510 acre-feet for joint use. The spillway is an open rock cut with a concrete control section having a capacity of 3,000 cubic feet per second. The outlet works, with a capacity of 1,000 cubic feet per second, is located in the right abutment.


Platoro Dam and Reservoir are located in a geologic area consisting of a complex volcanic bedrock material of, andesite, latite and related rock materials such as breccias and agglomerates.  In addition, a unique basaltic material and occasional intrusions are found in the area.  Land and rockslides of great magnitude dominate surficial geology.  There are two large fault zones that cross the basin at right angles, one about one-half mile upstream and the other about 3 miles upstream.  There are, however, three distinct shear zones within the dam and dike foundation area.  The damsite bedrock is severely fractured and contains localized shear zones.  Some of the shear zones contain highly stained or mineralized vein like material.  Exploration indicated the fractures were healed at depth and those that were opened were generally clean and free of mud or other material.  The dike and left abutment evidently lie in a huge postglacial rockslide.

RegionFacilities in Upper Colorado | Upper Colorado Home Page
ProjectSan Luis Valley
Dam TypeEarthfill
WatercourseConejos River
Location1 mile from Platoro, Co
Original Construction1949-1951
Modified Construction
National ID NumberCO1671
Hydrologic Unit Code

Structural Height165.0 ft
Hydraulic Height (Normal Operating Depth at Dam)139.0 ft
Top Parapet (Elevation)
Spillway Crest Elevation10034.0 ft
Crest Elevation10048.0 ft
Crest Length1,475 ft
Crest Width
Base Width
Volume of Dam Construction Materials
Streambed at Dam Axis9903.0 ft
Top of Exclusive Flood Control Pool (Elevation)
Top of Joint Use Pool (Elevation)10027.5 ft
Top of Active Conservation Pool (Elevation)10034.0 ft
Top of Inactive Conservation Pool (Elevation)
Top of Dead Storage Pool (Elevation)9911.4 ft

Hydraulics & Hydrology
Total Water Storage at Elevation
Maximum Water Surface Elevation10042.9 ft
Normal Water Surface Elevation10034.0 ft
Spillway Type
Auxiliary SpillwayNo
Spillway Capacity at Elevation3000.00 cfs at 10042.0 ft
Auxiliary Spillway Capacity at Elevation
Uncontrolled Spillway Capacity at Elevation
Outlet Works Capacity at Elevation710.00 cfs at 9963.0 ft
Diversion Capacity at Elevation
Drainage Area40.0 sq mi
Hydrometeorological Report (HMR)HMR 55
Probable Maximum Flood (PMF) Report

Contact Information
TitleArea Office Manager
OrganizationAlbuquerque Area Office
Address555 Broadway NE, Suite 100
CityAlbuquerque, NM 87102-2352
Phone (Office)505 462-3542
OrganizationConejos Water Conservancy
AddressPO Box 550
CityManassa, CO 81141
Phone (Office)719 843-5261

Last updated: Mar 26, 2009