One of my favorite subjects to photograph are streams, creeks and rivers of all sizes. I continue to take photos during all seasons of the year, and would like to offer some tips that I have learned over many years.
In spring and summer, the trees will of course have most of their full green foliage, and there may be other green vines, shrubs, etc along the water. I have found during these seasons, that it is best to expose a photo either on gravel/sand along the stream, or in the upper canopy of the trees where there is less full green color. If you expose on the deep green colors, it is likely there will be areas of your photo which are washed out.
During fall there will likely be some intense colors in the leaves, some of which are still on the trees and some likely will be on the ground. Again, don't expose on the darker colors, but use some lighter color such as gravel / sand or the lighter tree limbs, but not the darker tree trunks.
Winter photography can present some challenging conditions, especially if snow is on the ground. If there is snow with bright sunny conditions, either reduce your exposure by 1 to 2 stops, or use a snow scene setting on your camera. During cloudy and snowy conditions, it is best to expose on some yellowed grass or lighter branches in the trees. These photos may require some adjustment with a photo editing program to bring out the contrast and brightness.
In summary, it is best with all landscape photos to expose on areas which are medium light - your camera is usually set to get the best exposure with an 18% gray color. In fact, many photographers carry an 18% gray card to use to set the proper exposure.