Authorized Purposes
The six Mainstem dams, working together as a system, are Congressionally authorized to store and release water for eight purposes: flood control; navigation; hydropower generation; irrigation; water supply; water quality control; recreation; and fish and wildlife. Operation of the Mainstem Dams complies with all Federal Laws and the provisions of the 2018 Biological Opinion. Human life and safety are the priority in reservoir operations and serving the Missouri River system's authorized purposes.
Flood Control
The Missouri River Mainstem dams are designed to manage flood risk and reduce flood damages. As a runoff driven system, any water captured in the flood control storage zones of the dams each year, is what must flow out in that year. Current storage and release decisions are governed by the 2018 edition of the Master Manual providing guidance for Mainstem Reservoir System operations and are significantly designed around flood control and navigation purposes.
Hydropower
Releasing water from the dams serves multiple purposes including creating flood control storage space and serving the other authorized purposes such as hydropower, water supply, navigation, etc. More than 90% of releases from the Missouri River Mainstem System of dams passes through powerhouses to generate electricity.
A Hydropower Master Plan outlines future requirements for sustaining hydropower mission capabilities and guiding future programming and funding for hydropower sustainment, rehabilitation, and modernization requirements to provide predictable funding and maximize efficiencies to ensure the long-term resilience and reliability of this critical national infrastructure.
Garrison Dam began generating power in January 1956. The dam has five Francis turbines, which can generate up to 583,300 kW of energy. Three of the generators can generate 121,600 kW each and two can generate 109,250 kW each. On average, the project generates 2,285 million kWh of energy. The discharge capactiy of releases through the Garrison Dam powerhouse is 41,000 cubic feet per second allowing nearly all releases to generate electricity.
Navigation
The Missouri River Navigation Channel covers 734 miles, beginning at Sioux City, Iowa continuing to the mouth at St. Louis and is supported through Missouri River Mainstem System releases. Releases from Gavins Point Dam provide flow support for downstream navigation and releases from the upstream projects eventually pass through Gavins Point Dam. The Missouri River dams have no locks to accommodate navigation from one lake to another.
Flow support for commercial navigation is normally provided from late March to early December. Locations for measuring navigation flow targets include Sioux City, Iowa; Omaha and Nebraska City, Nebraska; and Kansas City, Missouri. Flow targets and the period for providing flows to support navigation varies by the target location, available system storage, and runoff conditions.
In addition to flow support for navigation, the Omaha and Kansas City Districts manage the Missouri River Bank Stabilization and Navigation Project which maintains a navigation channel that is a minimum of 9 feet deep and 300 feet wide at designated flow rates to provide adequate river depths and width.
Water Quality
Water quality is regularly monitored, reported, and managed consistent with Clean Water Act standards.
High reservoir levels or inflows may carry debris which can impact intake structures. Additionally, low reservoir levels or releases can impact water temperatures or cause a lack of oxygenation and dilution of pollutants, which typically occurs through reservoir releases.
Water Supply
The permanent pool zone of each reservoir provides minimum levels for power generation, irrigation diversion levels, and reservoir elevations to support water supply, recreation and fish and wildlife purposes.
Public and private water users maintain intakes to access water for uses including municipal, industrial, or personal use. Reservoir storage and releases from the dams that supply water to generate hydropower and support navigation also supply water for these purposes. Low water levels may require water users to lower intake structures to gain access to the water.
Irrigation
Among the intake structures placed in permitted locations along the reservoirs and in the river, is to access water for irrigation. Irrigators maintain their own intake structures for accessing the water. Equipment owners or operators should monitor water levels to take measures to reduce potential impacts to equipment.
Recreation
Fishing is the primary recreation activity at Lake Sakakawea. There are several boat ramps located around the lake, and most are in recreation or wildlife management areas. Shoreline Access Areas around the lake offer an additional access to the water’s edge. For information USACE-operated recreation at Lake Sakakawea visit Recreation.gov.
The Garrison Dam National Fish Hatchery and Visitor Center is located downstream of the dam. The Center’s five 400-gallon aquariums provide viewing of the fish of North Dakota in their environment.
The 14,739-acre Audubon National Wildlife Refuge provides several exhibits featuring wetlands, native prairie, and the abundant wildlife that can be observed across the refuge.
Fish & Wildlife
The Missouri River creates and maintains important forest and wetland habitat for diverse wildlife, including mammals, birds, reptiles and amphibians. The diversity and abundance of wildlife reflects a mix of Missouri River valley habitats including riverine; reservoirs, lakes and ponds; emergent, scrub-shrub, and forested wetlands; riparian forests; grasslands; and croplands.
USACE projects consider habitat needs when planning water resource development projects and may benefit fish and wildlife through modifications. USACE projects also support state and federal fisheries, wildlife refuges, and natural resource management programs.
Minimum releases that support navigation, hydropower, water supply and other purposes as well as naturally occurring activities such as spring plains snowmelt that leads to steady or rising reservoir pools also support fish spawning and hatching.
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