To summarize, the NMFS believes that at this time the best scientific evidence supports continuation of the established spring flow objectives and operational measures. The question of how summer-migrating juvenile fall chinook salmon respond to changes in both flow and temperature has also been extensively studied. Most recently, the NMFS has been involved in a study of the survival of Snake River fall chinook from above Lower Granite Dam to below Lower Monumental Dam. The results of these investigations between 1995 and 1997 indicate that survival during the summer months, when flows are low and temperatures reach the upper limits of what salmon can take, is not very good. However, these data also show a very good relationship between flow and survival, as well as between temperature and survival.
Juvenile fall chinook salmon survive at a higher rate under increased flows and lower temperatures.
The science on this issue is even more clear for the summer migration season than for spring. The second point I would like to make is the notable difference between the effects of the spring and summer operational requirements on other reservoir uses. In order to accomplish this, reservoirs are operated during the winter to be at their upper flood control limit by April 10 - the start of the spring migration season. It also results in fuller reservoir conditions in the early spring. The summer flow season is managed quite differently.