Waterfalls in our mountains seem to fade away when there have been no rains, so it is always opportunistic to have a camera handy when the waters are pouring off by the roadsides.  The smoothing effect that is so prized by photographers, eliminates the sparkle and the dance of the water.  So although, I admit to not knowing how to do the smoothing, I don't spend a lot of time trying to accomplish it. Let the water shine!