Merwin Boat Ramp provides access to Lake Merwin Reservoir on the Lewis River near Ariel, Washington, with amenities including a boat ramp, parking, seasonal bathrooms, and picnic facilities.

Note that reservoir water levels fluctuate significantly, which can affect boat access at times, and a launch fee applies on weekends.

The ramp also serves as a put-in point for paddlers, offering novice-level paddling with approximately 6 hours of paddling to the Columbia River mouth.