Fred and Loucille Dahmer Caddo Lake Preserve

Caddo Lake's wetlands are home to nearly 190 species of trees and shrubs, 93 different fish, 46 reptiles, 22 amphibians, 47 mammals and more than 20 mussel species. More than 220 species of birds, including dozens of neo-tropical migratory songbirds, find refuge here. The U.S. Fish and Wildlife Service has prioritized the area based on the high-quality habitat for migratory and resident waterfowl. Today, however, more than 40 of the native species at Caddo Lake and Big Cypress Bayou are endangered, threatened or rare. 

Big Cypress Bayou and Caddo Lake are also renowned for their recreational value, which helps fuel the local economy. Each year, the lake draws thousands of anglers and waterfowl hunters. Kayakers and canoeists can paddle through towering, moss-draped cypress trees, while wildlife watchers can search for hundreds of different species.

One of the major threats to the health of Caddo Lake is the growing presence of invasive plant species. While natural, seasonal flows can help with the management of these exotic plants, many non-native species are choking out native flora, like giant salvinia—a noxious, floating weed that can double in size every two to four days. Other troublesome invasive plants found here include hydrilla and water hyacinth.

When a dam was built upstream on Big Cypress Bayou to form the Lake O’ the Pines in 1959, plants and animals that had adapted over the millennia to the natural ebbs and flows of the bayou quickly found themselves at the mercy of the dam. Some flood and drought levels are important for fish spawning, cypress tree regeneration and the flushing of excess sediments and nutrients, which can negatively impact aquatic plants and animals. Without this seasonal variation of flows, wetland communities can become stressed. The management challenges at Big Cypress Bayou are exacerbated by a weir, or low-water dam, on Caddo Lake that prevents its drawdown during periods of drought. 

The Cypress Basin Flows Project was initiated in 2004 by a partnership between TNC, the U.S. Army Corps of Engineers, Caddo Lake Institute, the Northeast Texas Municipal Water District and many other organizations. Further spurring the environmental flow work at Caddo Lake was a partnership between TNC and the Corps, called the Sustainable Rivers Program—a pilot project launched in 2002 to protect river ecosystems downstream of multiple dams in 13 states. So far, the project is demonstrating that science-guided changes to dam operations can improve river health while maintaining—or even increasing—other services, such as hydropower generation, water supplies and flood risk management. The project at Caddo Lake began after the State of Texas made the decision that no new water rights would be granted to protect the water flowing in our rivers, lakes and bays. The state enacted a law (Senate Bill 3) to provide a process for setting aside water for in-stream flows in Texas.

Working with the Corps and other partners, TNC defined the ecosystem flow needs of Big Cypress Bayou and the Caddo Lake wetlands through an initial study. Following this, several of our flow recommendations were implemented on an experimental basis from 2006 to 2011. At a December 2011 workshop, the partners agreed to implement many of these flow recommendations on a continual basis for the next five years, as permitted by drought and water development. Partners are also developing and implementing a monitoring plan to evaluate response to these new flows. Research is currently ongoing to help the Corps determine how healthy flows can be restored and the feasibility of modifying the weir dam at Caddo Lake while continuing to meet water supply and flood control obligations.