The Willamette River Water Trail is a "trail" of sites that can be reached by canoe, kayak and other human-powered boats, along the Willamette River, in Oregon, stretching from Sauvie Island in the north to the Eugene area in the south.
In Oregon, all navigable rivers (such as the Willamette) are open to the public, including their banks below the high water line. Rivers and beaches being open to the public does not mean access to them is public, and in many places, the Willamette is bordered by private lands. The Willamette River Water Trail is a place where people can both access the water, through boat ramps, and a place where people travelling on multiday trips up and down the Willamette can camp for the night, either in campsites or in more primitive conditions. There are only a few state parks that have direct access to the Willamette, such as Luckiamute Landing, so most of the parcels along the 187 miles of the Willamette River that people can camp at are owned or managed by other entities, such as county or city parks. Many of them, such as the small gravel islands in the middle of the Willamette, are just state lands with no type of management or upkeep.
In fact, while researching this, I was unclear just who or what the "Willamette River Water Trail" is. Is there actually some sort of entity that maintains or oversees the park, or is it just a name for series of discrete units? There is a website, https://willamettewatertrail.org/, as well as an entry in the state parks database, https://stateparks.oregon.gov/index.cfm?do=park.profile&parkId=194, but it is unclear to me whether this is a central body that oversees the trail, or whether both of them are just collecting information on a preexisting series of parks, facilities and greenspaces. But in either case, for the dedicated river traveler, there are "approximately 83" different facilities along the Willamette River to enjoy nature and the river.