The Madawaska flows out of Algonquin park, and from Bark lake onwards, the flows are managed by a series of hydro dams. However, the upper section is almost unregulated so is best in the spring and early summer. It tends to flow later and for longer than the highway 7 runs. Most of the rapids are G3+, with 2 or 3 harder drops that can all be portaged.
There are a few rapids on the way out of Whitney, until Rapid lake is reached. Follow the right arm for about 3km to the outflow. For much of the rest of the river there is an old rail bed that follows the river on the right that is used for easy portage and inspection. Hermann's Chute is the first major rapid encountered, is quite long and has several fun lines on it. Further down, Bear Trap rapid is short, with a sticky hole to boof over and a rock on the right to avoid. Immediately afterwards, Little Niagra is reached - a riverwide fall with a considerable hydraulic. This is usually portaged, but the final drop can be snuck on the far left in low flows. This is the last of the difficulties.
To get to the take out; Turn off highway 60 in Madawaska onto Major Lake road, heading north. This is the first major intersection west of the bridge over the Madawaska. In 100 m, turn left to stay on Major Lake road, and follow for another 8 km to the bridge.
To get to the put in; Head back to Madawaska and turn right on highway 60. Follow this to Whitney, and park on the left immediately after crossing the river. Put on below the dam. There is an alternative put in that avoids the paddle across Rapid lake, but misses out on a few rapids. This is along McCauley lake road, about 5 km east of Whitney, and follows a hydro line cut. The road is likely to be in a fairly rough shape in the springtime.