Nelson Dam

Overview

The Nelson Reservoir, located 19 miles northeast of Malta, MT, provides offstream storage for irrigation of Malta Division lands in the Saco and Hinsdale areas. A series of dikes, with a maximum structural height of 28 feet, crest length of 9,900 feet, and total volume of 233,000 cubic yards, provide for storage of 79,200 acre-feet of water. The reservoir does not have a spillway. Slide gates installed in the Nelson North Canal outlet works permit releases of water to Milk River for use in the Glasgow Division. Slide gates installed in the Nelson South Canal outlet works permit releases of water for irrigation of project lands.

Preconstruction subsurface investigation efforts for the Nelson Dikes were limited to hand-dug pits along the footprint of the proposed structures. Investigations conducted since construction indicate all the structures were founded in unconsolidated and potentially liquefiable materials.


General
RegionFacilities in Great Plains | Great Plains Home Page
StateMontana
CountyPhillip
ProjectMilk River
Dam TypeHomogeneous earthfill
ReservoirNelson
WatercourseOffstream Storage
LocationFive dikes located offstream about 19 miles northeast of Malta, Montana.
Longitude-107.5221
Latitude48.5334
Original Construction1914-1915
Modified Construction Enlarged 1921-1922
National ID NumberMT00574
Hydrologic Unit Code

Dimensions
Structural Height28.00 ft
Hydraulic Height (Normal Operating Depth at Dam)20.00 ft
Top Parapet (Elevation)
Spillway Crest Elevation
Crest Elevation2,228.00 ft
Crest Length9,900.00 ft; (total length of all five dikes)
Crest Width 18.00 ft
Base Width166.00 ft
Volume of Dam Construction Materials 233,000.00 cu yd
Streambed at Dam Axis
Top of Exclusive Flood Control Pool (Elevation)
Top of Joint Use Pool (Elevation)
Top of Active Conservation Pool (Elevation)2,221.60 ft
Top of Inactive Conservation Pool (Elevation)2,200.00 ft
Top of Dead Storage Pool (Elevation)2,200.00 ft

Hydraulics & Hydrology
Total Water Storage at Elevation78,950.00 acre-ft at 2,221.60 ft
Maximum Water Surface Elevation 2,221.60 ft
Normal Water Surface Elevation
Spillway Type
Auxiliary Spillway
Spillway Capacity at ElevationNorth Canal: 250 cfs; South Canal: 500 cfs at 2,228.00 ft
Auxiliary Spillway Capacity at Elevation
Uncontrolled Spillway Capacity at Elevation
Outlet Works Capacity at Elevation
Diversion Capacity at Elevation
Drainage Area
Hydrometeorological Report (HMR)
Probable Maximum Flood (PMF) Report

Contact Information
Owner
TitleArea Manager
OrganizationMontana Area Office
AddressP.O. Box 30137
CityBillings, MT 59107-0137
Phone (Fax)406 247-7338
Phone (Office)406 247-7300
Operator
TitleArea Manager
OrganizationMontana Area Office
AddressP.O. Box 30137
CityBillings, MT 59107-0137
Phone (Fax)406 247-7338
Phone (Office)406 247-7300


Last updated: Apr 02, 2013