The Ramsar Convention's resources on Wetland Restoration

The STRP Expert Working Group on Wetland Restoration

Restoration Approach: Freshwater diversion

Wetland type: Marshes and swamps in subsiding deltaic systems or other systems with saltwater intrusion

Background: Construction of levees along the Mississippi River (and many other large rivers) prevent overbank flooding and the subsequent deposition of sediments in deltaic wetlands. Without repeated sediment deposition, deltaic wetlands subside and salt water intrudes into areas that were historically freshwater sites. Freshwater diversions pass freshwater through river levees to counteract salinization. In some instances, substantial structures (such as the Caernarvon Structure and the Davis Pond Structure, both in Louisiana, USA) are used to pass water through levees. In other instances, pipes are used (such as the Naomi Freshwater Diversion Siphon and the Violet Siphon, both in Louisiana, USA).

Advantages: Freshwater diversions reintroduce freshwater and to some degree sediment supplies to deltaic wetlands isolated from rivers by levees. Freshwater biological communities displaced by saltwater intrusion can quickly recover once salinities are reduced.

Disadvantages: Freshwater diversions can be expensive, and in many cases diversions do not introduce enough salinity to reverse subsidence of wetlands. Freshwater diversions require ongoing management and maintenance. After saltwater intrusion has occurred, viable and valuable saltwater biological communities may develop, and these communities will be displaced when freshwater diversions are installed. Diversions may cause erosion immediately downstream of their outlets.

Further Information: Various reports on diversions can be found at http://www.saveourwetlands.org/oldsite/techniqe.html. A web-based slide show on the Caernarvon Structure can be found at http://www.lacoast.gov/Programs/Caernarvon/caerwww/index.htm. Information on the Davis Pond Structure can be found at http://www.lacoast.gov/Programs/DavisPond/index.htm.

   The Davis Pond Structure under construction.

A drawing showing how the Davis Pond freshwater diversion will move Mississippi River water into wetlands currently cut off from the river by levees. Adapted from http://www.lacoast.gov/Programs/DavisPond/index.htm.

Return to STRP Wetland Restoration index page

For further information about the Ramsar Convention on Wetlands, please contact the Ramsar Convention Bureau, Rue Mauverney 28, CH-1196 Gland, Switzerland (tel +41 22 999 0170, fax +41 22 999 0169, e-mail ). Posted 8 January 2001, updated 15 February 2002, Bill Streever and Dwight Peck.