early spring when juveniles of most 

 estuarine-dependent species begin 

 moving into Louisiana estuaries. 

 Cooler temperature of diverted 

 fresh waters, as well as synergistic 

 effects of temperature and salinity, 

 could adversely affect growth and 

 survival of these populations. 

 Venkataramaiah et al. (1974) con- 

 ducted a series of laboratory experi- 

 ments with brown shrimp which clearly 

 demonstrated effects of interaction 

 between salinity and temperature. 

 Barrett and Gillespie (1973) reported 

 that the total number of hours of wa- 

 ter temperature below 20°C after the 

 first week in April appeared to be a 

 critical factor influencing brown 

 shrimp production in Louisiana. Ju- 

 venile brown shrimp survive and grow 

 best at salinities ranging from 15-20 

 ppt; discharge of cooler river waters 

 during periods of rising salinities 

 and temperatures could lower tempera- 

 tures and salinities enough to sig- 

 nificantly reduce production of brown 

 shrimp. Oysters can also be ad- 

 versely affected by synergistic ef- 

 fects of salinity and temperature. 

 Salinities below 5 ppt when tempera- 

 tures are below 20°C do not signifi- 

 cantly harm oysters. However, pro- 

 longed periods of salinities less 

 than 5 ppt when temperatures exceed 

 20°C can lead to high mortalities 

 (Lindall et al. 1972). 



WILDLIFE RESOURCES 



Primary adverse impacts on 

 wildlife resources would result from 

 excavation and dredged material dis- 

 posal due to construction of diver- 

 sion channels. It is estimated that 

 a typical diversion channel would 

 require a right-of-way approximately 

 500 feet wide for the channel itself, 

 berms, levees and disposal area. 

 Habitat types which would be impact- 

 ed include bottomland hardwood for- 



ests, wooded swamps and marshes. 

 Diversion routes under investigation 

 under the MLEA and LCA studies range 

 in length from 4 to 65 miles. 



CONCLUSIONS 



It is acknowledged that the 

 concept of freshwater diversion is 

 not without problems; however, cer- 

 tain measures could be taken to 

 lessen the severity of some of the 

 negative impacts. Adverse impacts 

 on fisheries resources could be 

 minimized by careful planning of the 

 design and operation of diversion 

 structures. If possible, water 

 should be diverted at a site in the 

 river where pollution is minimal; 

 however, this may not be feasible 

 from an engineering standpoint. 

 Benefits would be optimized by di- 

 verting water in late winter and 

 early spring before the majority of 

 juvenile organisms have moved into 

 nursery areas. Also, diversion 

 structures should be located far 

 enough from receiving water to allow 

 solar heating of diverted water. 

 Maximum heating could be obtained by 

 allowing overland flow through 

 marshes. This would have the addi- 

 tional benefit of stabilizing 

 nutrient concentrations and reducing 

 levels of toxic substances. In- 

 tensive water quality monitoring of 

 released water and receiving water 

 would be necessary through at least 

 two growing seasons. If high pol- 

 lution levels are observed in the 

 river, control structures could be 

 closed until water quality improved. 

 Animal and plant tissues should be 

 analyzed to determine the degree of 

 bioaccumulation of toxic substances. 



It is evident that coastal 

 Louisiana is experiencing severe 

 problems resulting from loss of 



383 



