You are stretching it to say there are 13 waterfalls in Yosemite Valley. Two well-known and year-round falls (Nevada and Vernal) are outside the immediate valley and require a hike to witness. The only two guaranteed year-round falls in the Valley are Yosemite and Bridalveil. There are numerous falls (like Horsetail) that appear in the spring after the snow melt . . . but soon "disappear." So please, readers, don't think you'll easily see a lot of waterfalls if you only tramp around the Valley.