Official guide and information to Lake Merwin boat rentals, jet skis, water sports, and lake tours at this reservoir in southwest Washington and is part of the Lewis River system. This popular body of water is home to huge Kokanee and Tiger Musky and Tiger Muskie for all you fishermen. Merwin Reservoir is a very popular Kokanee fishery because they often grow quite large so you can catch "the big one."
Enjoy all types of outdoor recreation including boating, watercraft, water skiing, the flyboard, wakeboarding, tubing, kneeboarding, wakesurfing, and more! There is a large campground on Lake Merwin it has RV hookups and tent camping sites. There are also a resort and marina facilities for day use areas. Merwin Reservoir is 4,090 acres near the town of Ariel, on the south side of Highway SR-503, is shared by Clark and Cowlitz counties.