The Conservancy and the U.S. Army Corps of Engineers are demonstrating that science-guided adjustments to dam operations and integrated floodplain management can increase benefits for people and nature. Pictured here is Oregon’s Willamette River.
Willamette River The Conservancy and the U.S. Army Corps of Engineers are demonstrating that science-guided adjustments to dam operations and integrated floodplain management can increase benefits for people and nature. Pictured here is Oregon’s Willamette River. © Bridget Besaw

Land & Water Stories

Sustainable Rivers Program

Modernizing Water Infrastructure to Maximize Benefits

An Opportunity for Change

For much of the 20th century, the United States built thousands of large dams and other water projects to meet the nation’s growing need for water, food, flood risk reduction, hydropower and navigation. But since their construction, the operations of very few public dams have been fully reviewed and updated to meet current needs. We now have the opportunity to modernize the operation of these water projects to improve the social, economic and environmental benefits they provide.

The Impacts of Altered Flows

Too often, river infrastructure like dams, locks and levees as well as the over-extraction of water and floodplain development disrupt natural flow patterns that are critical to the health of rivers and the flora and fauna that depend on them. Seasonal patterns of high and low flows support animal and plant lifecycles, preserve water quality and maintain diverse habitats. By artificially stabilizing river levels across the seasons, dams can set off cascading effects that negatively impact plant, fish and animal species, whole ecosystems and the diverse array of benefits they provide to people. Science has shown that altered rivers systems are much the reason why 40 percent of the nation’s fish species and 70 percent of freshwater mussel species are listed as imperiled, and why many commercial fisheries have been decimated.

With just 2 percent of our nation’s three million miles of rivers and streams still free-flowing and undeveloped, the survival of our freshwater systems hinges on our ability to reduce the negative impacts of river infrastructure.

Ebb & Flow: The Sustainable Rivers Program at Caddo Lake

Prescriptions for River Health 

In 2002, The Nature Conservancy and the U.S. Army Corps of Engineers—the largest water manager in the nation—launched a collaborative effort to find more sustainable ways to manage river infrastructure in order to maximize benefits for people and nature. First known as the Sustainable River Project (SRP), TNC and the Corps increased this work to eight rivers at 36 sites across the nation by 2015. In 2017, the Corps recognized the SRP as a line in their budget, and it became a “Program” that included, by 2019, 66 federal dams on 16 rivers in 15 states.

In short, the SRP focuses on determining unique flow requirements for rivers and then creating operating plans for dams that achieve environmental flows—scientific prescriptions for the timing, quantity and quality of water flow that must occur downstream and upstream of dams in order to revive and sustain critical ecological functions and habitat for species.

The Green River in Kentucky going through farms and forest.
THE GREEN RIVER in Kentucky is part of the Sustainable Rivers Program. © Mike Wilkinson

Support for Healthy Rivers

In a 2018 bi-partisan survey, 72 percent of American voters reported being seriously concerned about the health of our nation’s rivers and lakes. 

Sustainable Rivers Program Success Leads to Expansion

Today, science from SRP sites is proving that re-operating dams and modernizing other river infrastructure as part of whole-river systems increases the benefits they provide, particularly when done so in coordination with the downstream management of floodplains and other infrastructure. Furthermore, the benefits of these approaches have shown the SRP produces very good returns on investment.   

Because of the SRP’s proven track record, U.S. legislators recognized the value of the program’s many benefits—including its potential role in mitigating flood impacts—and in 2020 increased the nation’s annual investment in the program from $400,000 to $5 million. With this increased funding, researchers at rivers already in the program can expedite the testing of flow prescriptions and more quickly incorporate best solutions. Increased monitoring will also be used to help better understand the impacts of updated dam operations.

The additional funding will also enable the program to broaden the types of environmental actions to achieve the sustainable management of water and ecosystems at reservoirs. For instance, the Corps is working to adapt SRP methods for other infrastructure, especially locks and dams constructed on larger rivers where commercial barge traffic occurs. Other targeted infrastructure includes dry dams and that which impacts species listed as endangered or threatened under the Endangered Species Act.  

The program expansion is expected to bring the river count to the range of 26-31 rivers, exceeding the Corps’ Environmental Advisory Board challenge of 20 rivers by 2020.  

Map of U.S. showing rivers in the Sustainable Rivers Program
SUSTAINABLE RIVERS PROGRAM The rivers proposed for the SRP but in an exploratory phase are: several in Minnesota, including the headwaters of the Mississippi River; the Illinois River (OK); the St. Francis (AR/MO); and the Rio Chama (NM).

Potential for Nationwide Impact

Along with the work at the SRP sites, TNC and the Corps conduct joint training courses, research projects and staff exchanges to develop innovative water management software. The partners have also engaged dozens of public and private partners around the nation to share information and resources.

The SRP currently invests in 5,058 of river miles regulated by the Corps, but the program’s expansion could add another 6,319 river miles. The true value of the program, however, is its potential applicability to the more than 600 dams, 403 million acre-feet of water storage and almost 53,000 miles of river impacted by Corps dams.

A photo of the Roanoke River and rapids, surrounded by forests.
ROANOKE RIVER in North Carolina is part of the Sustainable Rivers Program. ©

Success Snapshots

  • TNC and the Corps first explored re-operating dams to better benefit people and nature at Kentucky’s Green River.
  • On Arizona’s Bill Williams River updated flow releases regenerated cottonwood and willow forests that flank the riverbanks and support a diversity of plants and animals, including nearly 350 species of birds.    
  • On Iowa’s Des Moines River changes to the management of at two dams will allow the Corps to periodically flood and expose mudflats to enhance nutrient cycling and provide improved habitat for migrating shorebirds and waterfowl.  
  • On the Roanoke River in North Carolina, new prescribed flows better mimic natural pulses, rather than creating prolonged floods downstream of the dam. Updated dam operations are helping restore the health of 95,000 acres of floodplain by reducing stress on bottomland hardwood forests and wildlife the forests support. The new flows also reduce the potential for dissolved oxygen crashes that lead to fish kills in the river. 
  • On some pools along the Upper Mississippi River, TNC works with the Corps to keep water levels just a foot or so lower during summer months, which exposes thousands of acres of mudflats and allows plants to take root. This produces big benefits for nature without affecting commercial barge traffic or other services the reservoirs provide. 

For more information, contact Gretchen Benjamin, a large river specialist at TNC.