How to photograph waterfalls to achieve the effect of flowing water, or the appearance of the"straw effect" in the water:
First off, you'll need a camera that allows you to adjust the shutter speed. The key to achieving the "straw effect", or flowing water, is to use a shutter speed somewhere between 1/15 second and up to a full second or longer. Assuming you have the right camera, then you'll need to shoot in the manual mode, or the shutter mode, so that you can set the shutter speed to one of these speeds. I would recommend taking a series of images, ie. 1/15, 1/8, 1/4, 1/3, 1/2, 1 sec. etec. Because you'll be shooting at a low shutter speed, you will also need a tripod to eliminate any camera shake. I also use a remote shutter release which will further reduce camera shake (movement). I've found that the best times of the day are early in the morning and on an overcast, or cloudy day. The other setting you'll want to experiment with is the ISO setting. Personally I prefer to shoot at the lowest ISO setting of 100, to achieve the lowest amount of grain, thus allowing you to enlarge your images without loss of detail. Good luck and happy shooting.