Overview
The Nelson Reservoir, located 19 miles northeast of Malta, Montana, 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
| Project | Milk River |
| Dam Type | Homogeneous earthfill |
| Location | Five dikes located offstream about 19 miles northeast of Malta, Montana. |
| Longitude | -107.5221 |
| Latitude | 48.5334 |
| Watercourse | Offstream Storage |
| Reservoir | Nelson |
| Original Construction | 1914-1915 |
| Modified Construction | Enlarged 1921-1922 |
| National ID Number | MT00574 |
| Base Width | 166.00 ft |
Dimensions
| Crest Elevation | 2,228.00 ft |
| Structural Height | 28.00 ft |
| Hydraulic Height (Normal Operating Depth at Dam) | 20.00 ft |
| Crest Length | 9,900.00 ft; (total length of all five dikes) |
| Crest Width | 18.00 ft |
| Top of Active Conservation Pool (Elevation) | 2,221.60 ft |
| Top of Inactive Conservation Pool (Elevation) | 2,200.00 ft |
| Volume of Dam Construction Materials | 233,000.00 cu yd |
| Top of Dead Storage Pool (Elevation) | 2,200.00 ft |
Hydraulics & Hydrology
| Spillway Capacity at Elevation | North Canal: 250 cfs; South Canal: 500 cfs at 2,228.00 ft |
| Total Water Storage at Elevation | 78,950.00 acre-ft at 2,221.60 ft |
| Maximum Water Surface Elevation | 2,221.60 ft |
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