FRESHWATER INTRODUCTION INTO LOUISIANA COASTAL AREAS 



John C. Weber and Robert A. Buisson, Jr. 



Department of the Army, New Orleans Distict 

 Corps of Engineers, New Orleans, Louisiana 



ABSTRACT 



AREA DESCRIPTION AND 

 BACKGROUND INFORMATION 



The conservation and enhance- 

 ment of fish and wildlife resources 

 through the control of salinities in 

 portions of the estuarine area of 

 Louisiana are the purposes of one 

 authorized project and two ongoing 

 studies in the U.S. Army Engineering 

 District, New Orleans. The primary 

 measure identified for controlling 

 salinities is to divert water from 

 the Mississippi River near the delta 

 to adjacent estuarine areas. Plan- 

 ning and implementing this type of 

 project presents a challenge from 

 both technical and institutional 

 standpoints. Technically, the 

 state-of-the-art for quantifying 

 benefits and impacts must rely on 

 expert judgment and assumptions. 

 From the institutional aspect, 

 freshwater diversion is supported by 

 many Federal, State, and local 

 agencies and organizations. However, 

 obtaining local cooperation and sup- 

 port for specific diversion sites 

 may be the most difficult problem 

 to solve because the local areas 

 where diversion facilities would be 

 located are not necessarily the 

 areas receiving significant benefits 

 from diversion. In some areas, 

 benefits may not outweigh adverse 

 impacts involved with constructing 

 and operating diversion facilities. 

 For the most part, benefits would be 

 widespread and would accrue to 

 interests not directly participating 

 in the project. 



The State of Louisiana contains 

 one of the Nation's most productive 

 estuarine areas. The area consists 

 of 363 miles of shoreline directly 

 fronting waters of the open Gulf of 

 Mexico (Becker 1972) and is pre- 

 dominantly composed of 4.2 million 

 acres of estuarine marsh lying at or 

 near National Geodetic Vertical Datum 

 (NGVD) (U.S. Army Corps of Engineers 

 1970). Pocked with numerous shallow 

 lakes and bays and interlaced with a 

 complex network of channels and ca- 

 nals, both natural and manmade, this 

 mixing zone represents a resource of 

 great value to the State and Nation. 

 It is estimated that there are nearly 

 30,200 total miles of shoreline in 

 the area, including the tidal shore- 

 lines of bayous, rivers, marsh lakes, 

 islands, and canals (Becker 1972). 

 The salinities of the waters in the 

 lakes, bays, and channels vary from 

 near zero to over 28 parts per thou- 

 sand, depending upon location and 

 numerous climatological , meteorologi- 

 cal, and hydrological factors. 



A unique feature of the estu- 

 arine area is its interrelationship 

 with the Nation's largest river, the 

 Mississippi. The average flow of the 

 Mississippi River into the area is 

 about 450,000 cubic feet per second 

 (U.S. Army Corps of Engineers 1970). 

 Below Old River, the Mississippi 

 transports some 300,000,000 tons of 



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