The document describes the water cycle and its importance. It explains that the sun heats water in the oceans, causing evaporation. Water evaporates from oceans, ice, snow, and plants. Rising air currents carry the vapor into the atmosphere where cooler temperatures cause condensation into clouds. Cloud particles collide and grow, then fall as precipitation in the forms of rain, snow, hail, fog or sleet. Precipitation runs off as snowmelt or surface runoff, infiltrating the ground to become groundwater or filling lakes and oceans, where the cycle repeats.