The Guardian reports:
Some say it looks like a a toilet being flushed; in more generous interpretations, it is a beautiful inverted fountain. In a rare occurrence, the water level in the Lake Berryessa reservoir, 75 miles north of San Francisco, has risen so much that it is pouring into a 200ft-deep circular pipe constructed in its corner. The 72ft diameter pipe, known as Morning Glory Spillway, or simply Glory Hole, takes in water like a drain, once the reservoir is filled over capacity, and shoots it into a creek below the Monticello Dam.
(Tipped by JMG reader John)