Removing Barriers to Reconnect Rivers

In cases where the value dams provide is outweighed by operational costs and the impacts to nature and people, TNC supports their removal. The removal of dams restores flows and the benefits they provide to people and nature. Obsolete dams can have a wide range of impacts on the environment and local communities, including loss of biodiversity, blocking fish migrations, trapping sediment and nutrients that maintain habitat and estuary health, and altering flow patterns that drive the productivity of downstream floodplains and wetlands. These impacts can affect public safety, food and water supplies, livelihoods, recreation and overall community well-being.

Or ensuring the “right fit.” More than 161,000 miles (260,000 kilometers) of free-flowing rivers are at risk of being impacted by the construction of new hydropower dams—equal to more than 39 times the length of the Nile. The impacts of these new dams would fall disproportionately in river basins with the greatest freshwater fish harvests and with the highest diversity of freshwater species, and—in many cases—greatly affect critical food sources for or displace Indigenous peoples.

Although dams can provide hydroelectric power, help reduce flood risk and store water to use later to irrigate crops, for drinking water and other purposes, their high ecological and socioeconomic costs mean they must prove their worth, and the case against them in our evolving energy sector is considerable. When and where new dams are proposed, we advocate for large-scale planning that factors in energy demand, other sources of renewable energy, project costs, and environmental and societal impacts. Our work within Brazil’s Tapajos River basin well illustrates this strategy put into action.

When roads cross streams—often over culverts—it can be problematic for the stream’s health and the safety of the road. Not only can poorly designed or undersized culverts hinder or block the migration of aquatic species, they can fail due to the increasing intensity of storms and growing development, which produces more runoff. TNC works with many partners to identify and fix problematic road crossings to enhance the movement of aquatic species as well as help road managers avoid tragedies, decrease much costlier emergency repairs and reduce expensive detours for travelers.

Explore examples of projects designed to address freshwater barriers that impact the movement of aquatic species, affect river health and impact people.

Obstacles aren’t an issue for aquatic species if there isn’t enough water to begin with. TNC employs an array of strategies aimed at improving or restoring “environmental” flows. Such work includes efforts to protect groundwater, modernizing the operations of dams, working with farmers to improve the efficiency of irrigated crops and the creation of water funds that help protect water sources and flows. See examples of such work.

• Helping shape Brazil’s hydropower future.
• TNC is helping remove obsolete dams and plan for new ones in Europe.
• Dam removals are helping “free” Kentucky’s Green River.
• Two dam removals and a fish passage made a big difference at Maine’s Penobscot River.
• Dam removals in Massachusetts brought back to life a “once-dead” river.
• Removing old dams created new hope for New Hampshire’s Bellamy River.
• Removing a dam helped improve the health of the Delaware River.
• TNC has prioritized dam removals throughout Tennessee.
• Removing “deadbeat” dams is reconnecting and restoring Vermont’s “broken streams.”
• TNC scientists recently detailed efforts to streamline culvert improvements in Maine.
• TNC received NOAA grants to improve culverts and bridges in North Carolina to improve fish passage and river health.
• TNC helped the State of Georgia produce a handbook to help improve the design of roads that cross streams.
• Tidal gates can also be a barrier for migrating fish; learn how TNC in Oregon addresses these to benefit salmon.
• This article published in TNC’s magazine provides an overview of work to address barriers to fish migration and the other impacts they have on people and nature.

• The restoration of 3,000 floodplain acres along 14 miles of the once-“channelized” Pocomoke River in Maryland.
• Nearly 150 projects in Oregon benefit salmon.
• Several projects in Ohio, funded through the state’s mitigation program, are improving river health.
• Projects in Arkansas benefit the Cache and Kings rivers.
• The reconnection of a 3.5-mile-long side channel along the lower Mississippi River.
• Restoring meanders to Montana’s Ruby River.
• Big lessons learned from the restoration of Little Creek in Missouri.
• Protecting and restoring Chinook and steelhead habitat in the upper Snake River in Idaho.
• Restoring spawning habitat in the Great Lakes.
• Restoring wetlands on Hawaii’s island of O’ahu.

• A 25-square-mile floodplain reconnection at “Mollicy Farms” along the Ouachita River in Louisiana.
• A 6,700-acre project at TNC’s Emiquon Preserve along the Illinois River in Illinois.
• A series of habitat reconnection projects on the Willamette River in Oregon.
• A 1,040-acre levee “setback” project along the Missouri River in Missouri.
• Work in Washington’s Puget Sound benefits salmon.
• Giving more room to the Sacramento River in California.
• Restoring tidal wetlands benefits salmon in Oregon.

• TNC is behind a myriad of efforts to protect groundwater that also supplies much of the flows in our rivers and streams. Learn more.
• The Sustainable Rivers Program improves the way many large dams are operated to produce more benefits and minimize environmental impacts.
• We work with farmers to reduce the amount of water they use to irrigate their crops. Our work in Nebraska, Arizona, Arkansas and other several states serve as prime examples of this strategy.
• We’re working to address water flows and water scarcity in a variety of different ways throughout the drought-prone Colorado River Basin in the U.S.
• TNC and its partners manage 32 Water Funds initiatives around the globe that provide a steady source of funding for the conservation of more than 7 million acres of watersheds and secure drinking water for nearly 50 million people. Colorado’s Yampa River Fund employs a variety of strategies aimed at protecting flows, and water funds we’ve helped launch in Africa and India that focus on agriculture improvements do as well. In Ecuador, two water funds are aimed at protecting water—and flows—at headwater sources.