

"\. 



JFMAMJJASOND 

 Month 



Walar Laval 



N D 



Figure 3-41. Water levels in Chenier Basin; (A) surface water slope in the Chenier and Mermentau basins from 

 U.S. Army Corps of Engineers data; (B) monthly variation in daily tidal range at Grand Chenier; 

 (C) seasonal variation in water level in Grand Chenier over a year; and (D) typical tide record. 



By far the major impact on natural wetlands has 

 been impounding. Over 10,000 ha (24,700 a) have 

 been impounded since 1952. These impoundments 

 tend to become increasingly fresh; their function as 

 a detritus source and as a refuge for estuarine species 

 is considerably decreased. Residual wetland loss to 

 inland open water habitat has been only about 0.1%/ 

 yr (912 ha or 2,254 a since 1952), comparable to the 

 Vennilion and East Bay basins. 



Urban and agricultural land use has reduced the 

 natural ridge habitat by 475 ha (1,174 a), a 12.6% 

 loss between 1952 and 1974. This unique habitat is 

 most fully developed in the Chenier Basin. 



Effects on renewable resources : The density of 

 estuarine-dependent fishery species is high in the in- 

 land open water habitat of the Chenier Basin (Perret 

 et al. 1971), and free water exchange with marshes 

 adjacent to the Mermentau River above upper Mud 



Lake does occur. However, access to marshes from 

 the lower Mermentau River is restricted and over two- 

 thirds of the Chenier Basin wetlands are now im- 

 pounded. The dependence of estuarine organism on 

 the linkage between marine waters and inland marshes 

 has been well documented, so it seems inevitable that 

 impoundments have seriously and adversely affected 

 these living resources. 



Estimates of waterfowl hunting compared to 

 waterfowl numbers in the Mermentau and Chenier 

 basins suggest that some increase in hunting is possible 

 without endangering these resources. These figures 

 must be interpreted with care, however, since they 

 are based on rather arbitrary assumptions about the 

 population served by these basins. 



Estimates of water quality made for the com- 

 bined Mermentau/Chenier basins indicated that load- 

 ing rates are high enough so that a borderline eu- 



119 



