This image shows water spiralling down a huge hole. But this definitely isn’t a gateway to another world. In reality, it’s simply a giant drain called a spillway to divert excess water.
Lake Berryessa in California, USA, can hold around 521 billion gallons of water – any more than that, and the excess begins to be drained off through the spillway. This year, for the first time in a decade, it rained so much in January and February that the lake reached capacity. Now the 72ft-wide hole is funnelling the extra water away to prevent flooding.
The mesmerising sight of the water plunging down the spillway has attracted hundreds of locals armed with cameras to capture this arresting phenomenon. It started on Friday 17 February, and could continue for another two weeks – more storms are expected, which should keep the spillway busy. There are many different types of spillways; the one at Lake Berryessa is a “bellmouth”, also known as a morning glory or plughole.
It works a bit like the hole in the side of a sink or bath tub, to prevent water spilling onto the floor if someone leaves the tap running. When it rains a lot and the water rises over 440ft above sea level in Lake Berryessa, it spills over the top of the hole, funnelling down and out into Putah Creek. The water was flowing at approximately two million gallons a minute on Tuesday – but it can flow much faster when needed.