Hydrological Cycle
The Water Cycle, also known as the hydrologic cycle, describes the process of how water naturally moves through Earth’s environment. Liquid water evaporates into water vapor (mostly from the oceans), condenses to form clouds, and precipitates back to earth in the form of rain and snow. Liquid water flows across the land surface (runoff), into the ground (infiltration), and through the ground (groundwater). Solid ice and snow can turn directly into water vapor (sublimation). Although the Earth’s water is constantly moving, it is instructive to determine about how much water is stored in each location at a given time. Water movement, distribution, and residence times will be explored in the first lesson of this series. The impacts of human activity on the water cycle will be explored in the second lesson. Because of the emphasis on groundwater in this lesson series, the third lesson deals with groundwater availability.
Water Cycle - Movement, Distribution, and Residence Times A short reading lesson on the Water Cycle (a.k.a. the Hydrologic Cycle) - how water is stored; how water flows between stocks; and how long water spends in various parts of the cycle. (Hydrological Cycle - 6)  
Human Influences on Groundwater Availability Prior to a recent knowledge about groundwater resources, it was commonly thought that groundwater was so isolated from the land surface that it was unaffected by human activities. As a more complete scientific understanding of groundwater developed, it became clear that large-scale agricultural practices and expanded urban centers created groundwater issues. Learn more in this introductory reading lesson! (Hydrological Cycle - 6)  
Groundwater Use & Availability How much fresh groundwater is available for use by society? How does this availability vary across the globe or at different times? What controls the availability/variability? Develop your own answers to these questions through this reading lesson! A few short questions are included to stimulate critical thinking. (Hydrological Cycle - 6)  
Unsaturated Zone Definition and graphic. (Hydrological Cycle - 6)