Hydrology's usually a bit of a dry subject. But when the study of water's movement across Earth helps us understand how waterfalls work, it becomes very dramatic indeed. Some of those visitors ...

We asked our readers to send in their best pictures on the theme of "waterfalls". Here is a selection of the photographs we received from around the world. Krzysztof Suchnicki took this picture of ...

Let's hope it doesn't melt! Spectacular images of adventurers climbing up frozen waterfalls Published: 13:17 EDT, 23 January 2014 | Updated: 13:58 EDT, 23 January 2014 ...