I like nothing better than to follow some bubbling rill up a mountain - it makes a delightful companion and almost always will lead me to a superb painting subject. Some of my most memorable moments in the hills has been climbing up a gill or gorge, staying as close to the water as possible, and often right in it! The combination of rocks and tumbling water I find irresistible, and in the current (July) issue of Leisure Painter Magazine you will find my article on painting moving, tumbling water.
The image shows part of a watercolour from my Mountains & Moorlands in Watercolour book, where a small cascade is falling between rocks. Painting cascades and waterfalls is all about contrasts: the contrast between the hard edges of rocks and the soft ones of the falling water where it passes in front of those rocks; and that of the white, aerated water against the wet, dark rocks. Too much of one or the other will weaken the effect. I also often break up the vertical elements with a small tree or branch, or perhaps a sprig of heather drifting in front of the falling water.
The preponderance of cool black - grey - blue - white can induce a feeling of cold austerity in the eye of the viewer, so in the above painting you will see that I've included a splash of red in the bottom right. One final tip: a few small flecks of white against the dark rocks and close to the falling water creates a sense of movement and splashing. You can do this with deft stabs with a scalpel, a few blobs of white gouache, or by spotting in some masking fluid before you start the painting, to reserve those tiny whites.
Another final tip: waterfalls are at their best after heavy rain, so get out there while it's still sloshing down for the best images, but be sure to keep all your accoutrements dry!!!