hi Stufish, I fished the Waitaki last weekend and had a talk to a few other people down there. They are catching some, but very few, with around 5-6 being weighed at the Glenavy hotel each day. Word is that the river is still too warm for a proper run and the fish that do enter the river aren’t too keen on the bite. I had no luck and only saw one other fish caught near the mouth which was a good one at about 10kg.
There is a good pool just up from the mouth (south side) which can be accessed on foot if you don’t mind wading, hard to explain exactly where but if you ask at the campground they may be able to point the access spot out to you. The farm road by the campground has access to ok water too.
I also paid the dam a visit but saw no fish apart from trout.
hope this helps – good luck!