I got out to the stream for four hours early this morning. I caught only two fish, but they were both good ones. Both were 21 inchers. These were the only strikes I had all morning so I was very fortunate to land both. Both were caught on bead-head mayfly nymphs. As JT talked about in another post, they were messing with the flows today. When I left home, the flow was 65 CFS. However, when I got the the stream (around 7:45), I had trouble trying to wade out to where I wanted to start; I backed off and started in a different location. When I got home, I found out that they had increased the flow from 81 CFS to 149 CFS while I was out there fishing. I'm sure this contributed to the tough fishing. Actually, it's a bit scary knowing that you could be caught mid-stream right at the time they are cranking up the flows.
I don't think there's a way to predict what the dam operators are going to do to the flows. This morning they LOWERED the flows. All you can do is check the flows before you go and see if there's a pattern (go to cdec.water.ca.gov/cgi-progs/queryF?=put for Putah flows). Also, be watchful when you are wading the stream that they could be raising the flows.
Looks like they will back down to 70 for the weekend, if their pattern holds. On the average, 100 cfs change in flow should change the average depth about 5" (calculated from height gauge on the Flow Charts) downstream. Surge near the dam could be much different.