Formed by Big Cypress Bayou, Caddo Lake – a natural lake – and its wetlands are made up of mixed bottomland hardwood forests and shallow bald cypress swamps covering more than 30,000 acres along the border of northeast Texas and northwest Louisiana. The area is one of only 27 wetlands in the United States recognized by the Ramsar Convention on Wetlands, an international treaty that recognizes exemplary wetland systems across the world. Caddo Lake 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. Over 220 species of birds, including dozens of neo-tropical migratory songbirds, also find refuge here. And 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 help fuel the local economy. Each year, the lake draws thousands of anglers and waterfowl hunters. Canoeists can paddle through stately, moss-draped cypress trees, and wildlife watchers can search for hundreds of different species.
The Nature Conservancy in Texas became involved in efforts to conserve Caddo Lake in 1990 when the organization received two land donations – 478 acres from local landowner Robert McCurdy and 589 acres from Judge John Paul Harkey – that were combined to create the Conservancy’s Fred and Loucille Dahmer Caddo Lake Preserve in 1997. The preserve was rededicated in 2001 to the memory of the late Fred and Loucille Dahmer, who lived at Taylor Island on Caddo Lake and spent much of their lives exploring and photographing the lake and working tirelessly to protect its fragile wetlands.
In 1993, the Conservancy and Texas Parks and Wildlife Department joined forces to purchase 7,000 acres to add to the 483-acre Caddo Lake State Park to create the Caddo Lake State Park and Wildlife Management Area. And, after years of work, the U.S. Fish and Wildlife Service opened in 2009 the Caddo Lake National Wildlife Refuge, initially comprising 7,500 acres.
When a dam was built upstream on Big Cypress Bayou to form the Lake O’ the Pines in 1959, plants and animals adapted over the millennia to the natural ebbs and flows of the bayou were, for the first time, at 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 ecosystems become stressed. The management challenges at Big Cypress Bayou are exacerbated by a weir, or low-water, dam on Caddo Lake that prevents its draw down during periods of droughts.
One of the major threats to the health of Caddo Lake is the heavy invasion of the lake by exotic, noxious plants. Today, natural, seasonal flows can also help with the management of these invasive plants, like the recently arrived giant salvinia, a noxious, floating weed that can double in size every two to four days, choking out native plants below. Other troublesome invasive plants here include hydrilla and water hyacinth.
Ensuring "Environmental Flows"
The Cypress Basin Flows Project was initiated in 2004 by a partnership of The Nature Conservancy, the U.S. Army Corps of Engineers, Caddo Lake Institute, the Northeast Texas Municipal Water District and many other organizations. Spurring the environmental flow work at Caddo Lake was a partnership between the Conservancy and the Corps called the Sustainable Rivers Project, 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 adjustments to dam operations can improve river health while maintaining – or even increasing – other services, such as hydropower generation, water supply, 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 for the protection of flows in 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.
After the Conservancy, working with the Corps and other partners, defined through an initial study the ecosystem flow needs of Big Cypress Bayou and the Caddo Lake wetlands, several of the recommended flows were implemented on an experimental basis from 2006 to 2011. At a December 2011 workshop, the partners agreed to implement much of the recommended flow regime on a continual basis for the next five years, drought and water development permitting. Partners are also developing and implementing a monitoring plan to evaluate response to these new flows. Research is also 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.