PrintAs we learned in Lesson 1, the storage reservoirs of groundwater greatly exceed those of atmospheric water vapor and precipitation, and the amount found in bodies of freshwater, such as rivers. About 22% of the world's population relies solely on groundwater for their daily needs, accessed primarily through dug or drilled wells (West and Odling 2014). However, there is a lot more to understand about groundwater than drilling a well and finding water!
As the term groundwater indicates, this source lies below the Earth's surface and, therefore, is more difficult to visualize and access. When precipitation or surface water infiltrates into deeper layers of soil or rock, this is known as recharge because the aquifer is gaining more volume. Conversely, when groundwater seeps or flows out onto the surface, or into a body of water, the term used is discharge. The origin, storage, and flow of groundwater are covered extensively in Chapter 5 of the text, so they will not be elaborated on here. Studying the diagrams concerning groundwater in Chapter 5 and in the Lecture 3.1 PPT will be especially useful for visualizing what is often a hidden and mysterious feature beneath the Earth's surface.
When people seek access to groundwater reserves, they most often dig (shallow) or drill (much deeper) a well. Qanats, the ancient water-yielding tunnels from the Middle East (Harvesting Water and Harnessing Cooperation: Qanat Systems in the Middle East and Asia | Middle East Institute (mei.edu)), demonstrate the level of sophistication possible in designing and engineering a complex infrastructure in arid regions, which was developed over 3,000 years ago. The drilling of wells in modern times requires a substantially different, but effective, technology.