To keep from having fish kills, discharges must be mixed with air or oxygen to bring DO levels in the tailwater up to a livable level for trout. Luckily it doesn't happen in all reservoirs, and in those where there is a problem, dam operations are usually modified to reduce the potential of a fish kill. Beyond the problem of low dissolved oxygen and cold water temperatures, most tailwater problems stem from conflicting interests. Nowhere has a dam designed and constructed to provide high quality trout angling. The fact that we have good trout fishing, bring millions of dollars annually to local economies, has little or no relationship to dam operation.
Daily flows go from flood to drought, depending on electrical or irrigation demands.
Some reservoirs are drained dry in drought years. The most recent threat to tailwater trout fisheries is the introduction of whirling disease. Word on the street says that the Beaverhead River is infected and we all know about the problems the Madison and the Colorado rivers are having with the disease. Once infected there is no cure. Prevention is the only course of action available to fisheries managers.