US Army Corps of Engineers
Institute for Water Resources

Bill Williams River, Arizona

Managing rare ecosystems in a unique natural setting

The Bill Williams River flows through the wild Arizona desert. Most of the river below Alamo Dam, the only major dam and reservoir in the watershed, runs through wholly undeveloped lands. This makes the Bill Williams a river of critical ecological importance and unique scientific opportunity in the Southwestern U.S., where most rivers are highly engineered for human uses. The Corps, Conservancy and numerous partner organizations are working together to better understand the connections between water and nature as part of an ongoing and collective effort to promote science-based stewardship of this rare oasis.

Alluvial valley reach of the Bill Williams River, Arizona. The Bill Williams River channel is characterized by a series of relatively narrow bedrock gorges separated by wider, alluvial reaches.
Bill Williams National Wildlife Refuge, Arizona. The Bill Williams River drains more than 5,200 square miles of rugged, mountainous terrain in west-central Arizona. It is the largest tributary of the Colorado River between the Virgin and Gila Rivers. The name “Bill Williams River” is applied to the river segment extending from the confluence of the Big Sandy and Santa Maria Rivers to the Colorado River confluence at Lake Havasu.
The Bill Williams River and floodplain are shown during a time of high release from Alamo Dam. High flows in the Bill Williams are critical for renewing riparian forest and maintaining channel habitat.
The Bill Williams National Wildlife Refuge, currently home to more than 300 species of birds with at least two more species coming in every year and an array of native riparian flora, benefits from water contained and released from Alamo Dam by the U.S. Army Corps of Engineers Los Angeles District, which entered an innovative partnership with state and federal agencies in the 1990s. Through the innovative partnership, known as the Bill Williams River Corridor Steering Committee, the District helps maintain a state park which hosts thousands of visitors every year and sustain 50 miles of downstream riparian habitat along the Bill Williams River all the way to Lake Havasu.
The water contained and released from Alamo Dam by the U.S. Army Corps of Engineers Los Angeles District, which entered an innovative partnership with state and federal agencies in the 1990s, helps maintain a state park which hosts thousands of visitors every year and sustain 50 miles of downstream riparian habitat along the Bill Williams River all the way to the Bill Williams National Wildlife Refuge. The Corps manages nearly twelve million acres of water across the country and is consistently seeking innovative and environmentally sustainable solutions to the nation's water resources challenges to help strengthen the nation.

Bill Williams River

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The Bill Williams River drainage area includes Alamo Lake, a U.S. Army Corps of Engineers, Los Angeles District reservoir constructed in 1968 and located in southwest central Arizona. Alteration of natural river flows resulting from the construction and operation of dams can result in substantial changes to downstream aquatic and bottomland ecosystems and undermine the long-term health of native species and communities. 

Land and water managers are examining ways to manage reservoir releases to produce flow regimes that simultaneously meet human needs while maintaining the health and sustainability of downstream biota. 

A new Water Control Manual was issued in December of 2003 through a collaborative effort that brought stakeholders together to endorse a new approach to managing Alamo Dam beginning in 1994.

Developing and implementing improvements to existing hydrologic models of reservoir operations, and a comprehensive adaptive management and monitoring plan to assess dam operations served as motivators to advance the understanding of the unique waterway and focus on the advancements made in river science.

“The goal is not to create optimal conditions for all species all of the time; rather, we want to create adequate conditions for all native species enough of the time."

Flow releases from Alamo Dam are adjusted to meet a variety of natural resource objectives, including the enhancing cottonwood-willow riparian areas and flood control. Similarly, implementing adaptive management through this approach facilitates evaluating management efforts and encourages making necessary adjustments to better achieve a sound balance between various management objectives upstream and downstream of Alamo Dam.

Alamo Dam was constructed under authorization of the Flood Control Act of 22 December 1944 (Public Law 534, 78th Congress, 2nd Session). The project was recommended for approval by the Chief of Engineers in his report dated 11 April 1944, published as a part of the project document (House Document No. 625, 78th Congress, 2nd Session). The project was authorized for flood control, water conservation, and recreational purposes. 

Subsequent legislation under Section 301(b)(1) of the Water Resources Development Act of 1996 (Public Law 104-303) authorized Alamo Dam to be operated for fish and wildlife benefits upstream and downstream from the dam.

  • Arizona Game and Fish Department - North Sector - Yuma Region(4)
  • Arizona Game and Fish Department - Aquatic Habitat 
  • Arizona State Parks - Alamo Lake State 
  • Arizona State Parks - Hydrology
  • The Nature Conservancy - Arizona Chapter
  • U.S. Army Corps of Engineers - Los Angeles District
  • U.S. Bureau of Land Management 
  • U.S. Bureau of Reclamation 
  • U.S. Fish & Wildlife Service

Publications

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TitleSiteDate
Bill Williams - Initial monitoring resultsBill Williams River2010
Bill Williams - Hydroacoustics and sediment coringBill Williams River2011
Bill Williams - Sediment dynamicsBill Williams River2013
Bill Williams - Assessment of in-lake fisheriesBill Williams River2015
Bill Williams - Environmental flows workshop reportBill Williams River2005
Bill Williams - Environmental flows science and workshopBill Williams River2006
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