Clams,
There is a dirt road on the west side of the reservoir just past the ranger station that runs down to the river below the dam. There are some other access locations between there and White Haven but you need to know where you are going. White Haven would have the next best access location.
Its nice water, very rocky like the gorge.
FYI - its a big Whitewater release weekend coming up, so you may want to pick a different weekend to try it out.