At this time of the year there may not be any white or wild waters in the area. Except possibly the Merrimack River below the Franklin Falls Dam after a good rain storm. I am not sure about the Swift River after the dam, but you can check it out.
At this time of the year, the best bets are the rivers in the Moosehead Lake area in Maine. All three are dam controlled and up to Class IV rapids.
If you want to paddle where there are 'ripples', less than Class I, I would suggest the Androscoggin River near Lake Umbagog. The scenery is incredible! The fishing is second to none!
Otherwise a leisurely paddle from the Lakeport dam down to Lake Winnisquam via the Winnipesaukee River will be your best bet.
Just be careful of fishing lines off the bridges.
