US Army Corps of Engineers
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Cossatot River, Arkansas - Exploring environmental flows to benefit fish and mussels

A group of state and federal fish and wildlife agencies is helping USACE’s Little Rock District develop new environmental flows at the Cossatot River in southwestern Arkansas. The Cossatot provides critical habitat for endangered species like the leopard darter, which needs need clean, cool, flowing water and gravel substrate to spawn.

Image of the Cossatot River

Cossatot River - The Cossatot River originates in Arkansas’s Ouachita Mountains. Waters of the Cossatot flow down the Little, the Red, and the Mississippi Rivers enroute to the Gulf of Mexico (USACE photo).
Image of Gillham Reservoir taken at sunset (or sunrise) from the shore

Gillham Reservoir - The surface of Gillham Reservoir extends over 4,700 acres and provides boating, fishing, swimming, and other outdoor recreation opportunities (USACE Photo).
Image of meeting participants sitting and conversing around a rectangular table.

Defining Environmental Flows - Scientists, water managers, operators, and planners work to quantify flow needs of freshwater mussel species in the Cossatot River (photo by Jim Howe, The Nature Conservancy).

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The Ouachita Mountains stretch across western Arkansas and southeast Oklahoma, spanning the state line. This is a remote and heavily forested area, with 1.8 million acres of national forest – the Ouachita National Forest – and six wilderness areas.

In the southwest corner of Arkansas, five rivers race south through the ridges and valleys of the Ouachitas before slowing in the lowlands of the Gulf Coast. The rivers converge in the Little River, which flows into the Red and then the Mississippi Rivers.

In 1927, a massive flood decimated the Mississippi Valley. Floodwaters reached 30 feet in some communities. The Great Flood of 1927 prompted a wave of dam-building by the U.S. government, including several dams on rivers draining the Ouachitas. These dams allow USACE to hold back water in the event of potential flooding in the Lower Mississippi.

The Cossatot River is home to one of these dams. Highly scenic and popular among paddlers and anglers, the Cossatot is flashy and fast in its headwaters with plenty of Class IV and Class V whitewater.   Read More

  • USACE Little Rock District
  • Arkansas Game and Fish Commission
  • Arkansas Natural Heritage Commission
  • U.S. Fish and Wildlife Service
  • The Nature Conservancy
  • Arkansas Division of Environmental Quality
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