As realist painters we are often attracted to images and scenes that seem far too complicated to translate into watercolor. We look at all that specific information and throw up our hands in surrender.
I'm convinced it's becoming specific prematurely that makes things difficult. If you're painting a forest, don't build it tree by tree. Look for a way to see the whole subject rather than the components. It's easy to get hung up on how this particular tree is different from the adjacent trees. This is what Mary Whyte calls "taking inventory". Instead, try looking for the similarities first. Make general statements, then move toward specificity as needed.
By far the most significant feature of these trees is their color, and, as it happens, this is something they all share. Let's look at the big yellow shape that comprises most of the top half of the image.
Is there a way to paint the shape with an overall wash that can underlie everything that will come later?
Yes, the entire shape can be covered with a rich yellow wash, except a few whites that may be saved here and there. The yellow is a little greener in places, and a little redder elsewhere. It might be good to add a little of those colors (just a little) in a couple of places.
The second most noticeable feature of the yellow shape is the array of middle value strokes that are throughout. If you want some of them to have soft edges start making them while the yellow is still wet.
What proportion of the yellow shape will be given the middle value shadows?
I'd say about 15%
How are the middle value marks distributed throughout the big yellow shape?
Many are concentrated along the bottom edge of the yellow shape. A few are dispersed in the center, and some small marks in the upper area
Is there any pattern to the shapes? What kind of shapes are they? Horizontal? Vertical? Rectilinear? Organic? Hard-edged? Soft? Most of the stories are horizontal.
You can proceed to make the final layer, the darks, by asking the same questions about those skinny, dark vertical lines that are throughout the yellow shape; Proportion, distribution and pattern.
The answers to these questions are all abstract. They apply to form rather than content. Staying abstract may seem risky, since it can feel like there's no guarantee that the finished treatment will add up to a recognizable subject. Think of it as an act of faith, and put it's not your job, anyway to make sure the viewer knows what they're looking at.
By the way, how will the bottom of the painting differ from the top?
Here's another complex subject that would benefit from staying abstract. Squint!
Practice a lot, then see if you can stay abstract all the way to the end of a quick, simple version of one or the other of these scenes.