Nov 25, 2012 - 10:29 AM
Just as the snow is finishing melting at lower elevations, usually June. However, you will never see all 72. Some of them are barely a trickle of water down the mountain, not really visible but I guess "counts" as a waterfall for those doing the counting.
You can always see Staubbach (just outside of Lauterbrunnen) and the fall at the end of the valley (above Obersteinberg).