The model you see here is very similar to illustrations you will find in many textbooks. It shows the sizes of the different stores of water (e.g. 12.7 thousand cubic kilometres of water in the atmosphere as shown by the number inside the cloud) and the rates at which water moves between the stores (e.g. 2.5 thousand cubic kilometres of water moves from ice-sheets into the oceans every year as shown by the black arrow). The difference is, with this model, you can change things. It’s not a static illustration of the present Earth but a dynamic model of possible Earth’s. Play with it using the Simulation item on the Water Cycle menu to see what happens but first look at the Tutorial item on the same menu.