Northwest of Poughkeepsie near Hancock, the West Branch of the Delaware River is best known as an excellent tailwater fishery below Cannonsville reservoir.
The upper section is about 43 miles long from the headwaters in Schoharie County down to the Cannonsville reservoir. The primary river access is provided by SR10 which runs parallel. You can expect to find a few wild brook trout and stocked brown trout.
The more popular lower section begins at the Cannonsville reservoir and runs down 20 miles to the confluence with the main Delaware River. This is a popular tailwater fishery providing cool water year-round. You can expect to find plentiful brown trout in the 12 to 16 inch range. There are very few rainbow trout since the water is too cool. The fly fishing access for the lower section of the West Branch of the Delaware River can be found at Hancock, or by starting at the SR191 bridge and turning right on Winterdale Road which follows most of the river (public access starts when the road turns to gravel).
Overall, West Branch Delaware River is the 13th most popular fly fishing river of all 32 fly fishing spots in New York.