Dworshak Dam and Reservoir

Dworshak Dam is straight-axis concrete gravity dam with a structural height of 717 feet. It is the third tallest dam in the United States and the tallest straight-axis concrete dam in the Western Hemisphere.

Congress authorized the project for flood control, hydropower generation, outdoor recreation, navigation, and fish and wildlife benefits.  Today, we continue to operate for these purposes to benefit the public.

The lands around the 54-mile-long reservoir, located on the North Fork Clearwater River, include a variety of recreational opportunities, including fishing, boating, hiking, horseback riding, ATV riding, mountain biking, geocaching, camping, or wildlife watching.

Project Information

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Dworshak Vegetation Management

 Dworshak National Fish Hatchery

Dworshak National Fish Hatchery was constructed by the U.S. Army Corps of Engineers to mitigate fish losses associated with the construction and operation of Dworshak Dam. The fish hatchery started operation in April 1969. A Memorandum of Understanding was signed by the Corps and the Fish and Wildlife Service in 1969 authorizing the Fish and Wildlife Service to operate Dworshak National Fish Hatchery with reimbursable funding from the Corps. Since 1969, Fish and Wildlife Service has operated Dworshak National Fish Hatchery and has endeavored to meet the "mitigation goal" of maintaining the North Fork of the Clearwater River "B" run steelhead and producing resident fish for stocking Dworshak Reservoir.

 

Dworshak National Fish Hatchery Complex is located at the confluence of the North Fork and mainstem Clearwater River in Ahsahka, Idaho, 3 miles west of Orofino, Idaho. The Complex consists of Dworshak National Fish Hatchery, Idaho Fishery Resource Office, Idaho Fish Health Center and the Kooskia National Fish Hatchery located at Kooskia, Idaho (managed by the Nez Perce Tribe).  Dworshak hatchery production is co-managed by the U.S. Fish and Wildlife Service and the Nez Perce Tribe.

 Project Pertinent Data
General
River mile - 1.9
Drainage area - 2,440 square miles
Effective hydraulic height - 632 ft
Maximum structural height - 717 ft
Overall length at crest - 3,287 ft

Streamflow, cubic feet per second (cfs):
Minimum of record - 250 cfs

Standard project flood peaks:
Mean annual - 5,727 cfs
Winter - 160,000
Spring - 120,000
Maximum of record - 100,000
Probable maximum flood - 411,000

Streamflow, acre-feet:
Minimum annual - 2,157,000
Mean annual - 4,100,000
Maximum annual - 6,680,000

Project design discharges, cfs:
At pool elevation 1445 - 32,290
At pool elevation 1600:
Spillway – 150,000
Outlets – 40,000
Total at elevation 1600 – 190,000
220,000

Tailwater elevations:
Minimum, discharge 1,000 - 968 cfs
Maximum, discharge 150,000 - 1,003.4 cfs
First power online - 1 March 1973

Estimated Cost
1 July 1973 - $302,000,000

Reservoir
Elevations, feet:
Maximum design pool - 1605
Maximum operating pool - 1600
Normal operating range - 1600 to 1445
Storage capacity, acre-feet:
Gross - 3,468,000
Usable, flood control and power - 2,016,000
Length at elevation 1600 - 53.6 miles
Shoreline length - 175 miles

Surface areas, acres:
At elevation 1600 - 17,090
At elevation 1445 - 9,050

Recreation sites, number:
Initial - 7
Ultimate - 19

Non-Overflows
Type - Concrete gravity
Crest elevation - 1613
Deck width - 44 ft
Concrete volume - 6,500,000 cubic yards
Upstream slope - Vertical
Downstream slope - Vertical above elevation 1560, 1 on 0.8 below
Elevators, number - 3

Spillway
Type - Gate controlled, with stilling basin
Gates:
Type - Tainter
Size, width by height, feet - 50 x 56.4
Number - 2
Crest elevation - 1545
Crane capacity - 150 tons

Permanent Outlet Works
Water passages:
Number - 3
Type - Conduit
Size - 12 x 17 ft

Gates, type and number:
Tainter - 3
Tractor (emergency) - 1
Intake centerline elevation - 1362

Powerplant
Initial installation:
Number of units - 3
Nameplate rating, kilowatts:
Two, each – 90,000
One – 220,000
Total – 400,000
Ultimate installation:
Number of units - 6
Nameplate rating, KVA:
Two, each – 90,000
Four, each – 220,000
Total – 1,060,000
Powerhouse length - 428 ft
Turbine type - Francis

Turbine ratings, horsepower:
Small units - 142,000
Large units - 346,000

Synchronous speed, revolutions per minute:
Small units - 200
Large units - 128.6

Distributor centerline elevations:
Small units - 969
Large units - 975

Spacing, feet:
Small units - 47
Large units - 65

Penstock diameters:
Small units - 12
Large units - 19

Penstock intake elevations:
Small units - 1,420.68
Large units - 1,412.70
Gross head - 632 ft
Rated head - 560 ft
Minimum head - 477 ft

Crane:
Number - 2
Type - Bridge
Capacity, each - 350 tons

Relocations
Roads, miles:
Highway districts - 2.7
County - 24.3
Bridges, number - 2


Fish Hatchery, Steelhead
Attraction water pump capacity – 255 cfs
Capacity, adult size – 6,000 cfs

Yearly fingerling release:
Estimated number – 3,360,000
Estimated total weight – 420,000 lbs

Contact Us

Dworshak Dam and Reservoir
PO Box 48
Ahsahka, ID 83520-0048
 
Phone: 208-476-1255
 
Visitor Center Staff
208-476-1255
24-hour Information
800-321-3198
 
Big Eddy Marina Information
208-476-5994
 
Dworshak State Park
208-476-3132

Want to host an special activity/event?

Thinking about organizing a fishing tournament, family reunion, or some other event?

Email DworshakRecreation-NaturalResources@usace.army.mil to receive a special use application.