Correcting “failed” paintings in watercolor can be done with the addition of a little opaque paint. Keep in mind that watercolor paper is flexible and opaque paint is not. Opaque paint added too thickly will eventually crack. I will sometimes use acrylic white paint which remains flexible and can be used more heavily.
This waterfall composition is done on Arches 300lb paper. The final painting is okay, but not as dynamic as I had planned.
To get more contrast, I darkened the darks in the background and changed the shapes of some of the rocks. I also darkened the rock near the center of interest, and added more water flow with the opaque white paint on the left side of the painting.
In the middle ground, I darkened and made the one rock on the left a bit warmer to bring it forward. Paying attention to the flow and movement of the water I added some opaque white.
The most difficult correction is in the large rock in the foreground. It is already very dark and large. Adding too much opaque paint would make it too different in relationship to the rest of the painting. I did darken it enough to break it into some smaller shapes and then lighten the top with some translucent paint for more form.
I darkened the area flowing around the rocks and then added more movement in the water as it flows to the left in the foreground.
The final adjustments are subtle. The white space at the bottom was painted to match what is happening in the flow of the water.
I added more opaque white paint to the highlights making sure that they were not as white as the whites in the center of interest.
The final painting, although not compositionally much different than the original, is much more dramatic.