Waterfalls have become a favorite subject of mine to shoot, especially in the spring as there is more water volume and the soft green colors add a special light and touch. A cloudy or partly sunny day is perfect for getting the smooth, milky look of the water flowing. I prefer shutter speeds of 1.5 to 2 seconds as there is still some detail in the falling water left. Using a polarizer or neutral density filter is a necessity to slow down the shutter speed, and a tripod of course!
The first 2 photos are taken at Devil's Kettle in the Blue Hills (near Weyerhauser). The next 2 are at Houghton Falls near Washburn and the last are Morgan Falls - all in Wisconsin.