The Critical Zone

Summary and Final Tasks


This lesson on groundwater was crafted to introduce you to the fairly complex concepts of hydrogeology and groundwater flow. You should understand that some water that arrives at Earth's surface infiltrates into the ground. An unsaturated zone exists between the ground surface and the water table, beneath which lies the saturated zone of groundwater flow. Where recharge to the water table occurs freely without barriers to flow, unconfined flow systems exist. In some places, groundwater is confined—disconnected from overlying solid material and water outside of its recharge area. Surface water and groundwater can be in hydrologic communication in other ways, for example as gaining or losing streams.

Groundwater flows through spaces in the sediment and rock beneath our feet: a continuum exists in flow regimes between diffuse flow and fracture or conduit flow. Groundwater quality is affected by natural and anthropogenic processes. In some places, groundwater can be naturally degraded by proximity to geologic materials, but the majority of groundwater quality concerns are due to human activities, such as agriculture, industry, and waste disposal. Because of water's role as a solvent, and its intimate relationship to the sustenance of life, all of the processes you've learned about in this unit are important for furthering your understanding of Critical Zone processes. Remember, agua es vida.

Reminder—Complete all of the lesson tasks!

You have finished Lesson 7 and Unit 4. Double-check the list of requirements on the Lesson 7 Overview page to make sure you have completed all of the activities listed there before beginning the next lesson.

Tell us about it!

If you have anything you'd like to comment on or add to, the lesson materials, feel free to share your thoughts with Tim. For example, what did you have the most trouble with in this lesson? Was there anything useful here that you'd like to try in your own classroom?