You can photograph the river numerous ways. You can take large scenics with the river in the foreground and the cliffs and landmarks in the background, or you can zoom in and take an intimate detail of the river flowing over rocks or boulders as it flows west.
Looking for the best lighting and taking advantage of the best times of the day when the light is the most even on the water give you the best pictures. You want to avoid contrasty light when photographing the river.
You can use any lens you have to photograph the river. If you plan on doing longer exposures to get the feeling of movement through the water, your tripod will be a big help. And several filters are useful when photographing the river.
Wide-angle lenses give you broad views and put the river in the surrounding landscape. This way you can put the river in context with the cliffs and domes of Yosemite Valley.
Telephoto lenses enable you to isolate little cascades, ripples, and pools, letting you get close and intimate with the subject. So many variations are applicable here.
The most useful filters you can use when photographing the Merced River are a polarizing filter, a graduated neutral density filter, and a neutral density filter.
Polarizing filter. Useful for reducing glare and reflections off the surface of the water and rocks.
Graduated neutral density filter. Useful for balancing your lighting ratios, especially when ...