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Pishkun Dikes
Pishkun Dikes

Statistics

General

  • Region (Map) : .................. Great Plains
  • State (Map) ........................ Montana
  • County ................................ Teton
  • Project: ................................ Sun River
  • Dam type: ........................... Earthfill
  • Location: ............................ 20 mi. NW Fairfield
  • Watercourse: ..................... Offstream Storage
  • Reservoir: ........................... Pishkun
  • Construction Date:.............1914-1917
  • Enlargement Date:..............1930-1939
  • National ID Number .......... MT00575
  • Hydrologic Unit Code .....

Dimensions

Hydraulics

  • Normal Water Surface Elev: ................4370.0 ft
  • Hydraulic Height: .............................. 5.0-37.0 ft
  • Service Spillway Type: ............................. None
  • Morning-Glory .............................................. NA
  •    Crest Length    ........................................... NA
  •    Gated      ...................................................... NA
  •    Capacity at Elev: ........................................ NA
  • Auxiliary Spillway ......................................... NA
  •     Capacity at Elev.   ..................................... NA
  • Outlet Works Capacity at
  •     Elevation  4,371.2 ft,  ....................... 1850 cfs

Hydrology

  • Drainage Area: .................................... 9.7 sq mi
  • Hydrometeorological Report            HMR 55A
  • Flood Type: ........................................... General
  • Storm Duration: ........................................ 72 hrs
  • Probable Maximum Flood (PMF) Report:
  •   Peak Inflow: ...................................... 37,120 cfs
  •   Inflow Volume: ........................... 13,890 acre-ft
  •   Flow Duration: ......................................72 days
  •   PMF Routing MWS Elev:
  • Gates Closed ........................................ 4378.9 ft
  • Gates opened ......................................  4374.9 ft
  •   Initial Routing Elev:............................4370.0 ft
  •   Study Date: ............................................... 1988

Power Generation

Narration

 

Geology

Pishkun Reservoir and enclosing dikes are founded on glacial deposits (till) of an outwash plain lying east of the Sawtooth Mountains.  The thickness and character of glacial till vary widely over short distances.  Till was deposited by advancing ice and runoff fed by melting alpine glacier.  The thickness range is suggested by the hummocky topography characterized by rounded hills and undrained or poorly drained depressions.  The landscape just west of Pishkun Reservoir is dotted with small lakes and is generally poor drainage.  The reservoir and dikes are at the eastern margin of the glacial outwash plain.  Locally, erosion has cut through glacial deposits exposing shale and sandy shale of the Two Medicine formation.  The thickness range of glacial deposits under and around the reservoir is not well known but may range up to 100 feet.

Links

 | Recreation |

 | Dams Located by State | USBR Montana Dams | North Great Plains Region Dams |

 | Owner:  Bureau of Reclamation, Montana Area Office,
                   PO Box 30137, Billings, MT 59107-0137, (406) 247-7664

 | Operator:  Greenfields Irrigation District,
                       Box 157, Fairfield, MT 59436, (406) 467-2533

 
 

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