Pascagoula Tributary Dams: Chipping Away at the Jewel

The proposed dams on Big Cedar Creek will impact natural thermal refuges for fish in the Pascagoula River.

Pascagoula River | Brian Carlisle

Guest post by Andrew Whitehurst is a part of our America’s Most Endangered Rivers® series spotlighting the Pascagoula River.

The Pascagoula River is Mississippi’s ecological jewel.

In 1994, an article in Science noted a stunning statistic — the Pascagoula is the last river of its size class in the contiguous U.S. without a dam on its main channel. Of all the large rivers in the lower 48 states, the Pascagoula River stands alone without this type of major alteration.

One Chip, Two Chips

Unfortunately, development proponents have proposed plans for creating two new dams on a Pascagoula tributary called Big Cedar Creek. Designed to form two recreational lakes, these dams are currently undergoing a scoping process with the U.S. Army Corps of Engineers. Local government sponsors in George County, Mississippi, are pitching these recreational amenity lakes as backup water supply to the Pascagoula River during droughts. If damming happens, it will chip away at the special nature of the Pascagoula system. This threat is so great that it landed the Pascagoula on the 2016 list of America’s Most Endangered Rivers®.

Threatened Gulf sturgeon in the Pascagoula. | USFWS Endangered Species
Threatened Gulf sturgeon in the Pascagoula. | USFWS Endangered Species

The Pascagoula has been studied by scientists over many years. Threatened species that live in and along the river have been the subject of some of that research, including the yellow-blotched sawback turtle and the Gulf sturgeon. In addition, a historically abundant species, the striped bass has been restocked in the Pascagoula and other coastal rivers and has been the subject of ecological study. From 1997 through 1999, one group of researchers fitted striped bass with radio tags to track their movements and pinpoint thermal refuges or “cool spots” in the Pascagoula River where adult fish congregated during the summer months. Three such places were found, but the best one was upstream of the river’s tidal zone at the mouth of Big Cedar Creek. Big Cedar Creek has cool water flowing from the many springs that contribute to its base-flow. This thermal refuge was used by radio-tagged striped bass over two years to beat the summer heat. Fish are cold-blooded and regulate body temperature by seeking out water with a temperature range compatible with their metabolic requirements. That same study from researchers at Mississippi State University offered management recommendations to protect striped bass from overfishing while they congregated during the summer in cool water refuges in the Pascagoula River.

The research findings that Big Cedar Creek delivers cool water to the main river channel and that fish in the river use it to endure summer’s heat are two important reasons why altering the natural flow and function of the Pascagoula system with dams is likely to have significant environmental impacts. This is explained by considering the ecology and chemistry of reservoirs. Lakes behind dams reliably do two things: they trap sediment and they change the temperature of water released by their floodgates to channels downstream. The outfall of the lower proposed lake on Big Cedar Creek is close enough to the Pascagoula River that warmed reservoir water will likely raise the summer temperature of the cool spot in the Pascagoula at the Creek’s mouth. Just like that— the river’s best thermal refuge is lost. Fish won’t take refuge at the mouth of Big Cedar Creek in summer if the water there is as warm as, or warmer than other places in the river.

The loss of the cool spot in the river at the mouth of Big Cedar Creek is only one of many alterations that would accompany dam building. Communities should expect to see a degradation of the physical and biological quality of Big Cedar Creek, its associated wetlands, the adjacent Pascagoula River, and impacts to the species that call these special places home. Along with the proposed recreational lakes, promoted under the guise of “helping” the flow of the Pascagoula in future droughts, we can expect the loss of many of the characteristics that have made the Pascagoula River and its tributaries special.

Please take action today and let the Army Corps know that you do not support this unnecessary and environmentally harmful project. Comments close February 6th.

Andrew is the Water Program Director at Gulf Restoration Network. Gulf Restoration Network is committed to uniting and empowering people to protect and restore the natural resources of the Gulf of Mexico Region of the U.S.

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