If you are planning to visit Park City this summer for some rafting/kayaking, one suggestion would be the Jordanelle reservoir, though the best place for kayaking would probably be the Rock Cliff area, the Provo river (Vivian park area). You can also do tubing on the Weber River at Henefer/Taggart spots
If you plan to kayak at Vivian Park, be sure to pull out on the river left side of Vivian Park before going under the South Fork Road bridge because River right is private property. There will be large rocks and concrete blocks to help get out of the water.
rafting across the Dinosaur National Monument I remember doing some whitewater rafting across the Dinosaur National Monument along the Green and Yampa Rivers...The most challenging sections but also the most fun were the rapids at Warm Springs and Hells Half Mile. If you prefer calmer rides go on Rippling Brook or Island Park.