Take a look at the following diagram. It is a break down of the freshwater sources on Earth.
USGS: Water Science for Schools
Notice that just over ¾ of the freshwater is frozen in glaciers (77%). The other ¼ is groundwater (22%), rivers,
lakes, and atmosphere and soil moisture (all together these last sources make up less than 1% of the freshwater on Earth).
Now think about this:
Chapter 10 is about groundwater, that is, water beneath the surface that may or may not be available, or accessible
for use by humans. As you can see from this diagram, groundwater comprises about 1/5 of the freshwater on Earth.
Groundwater is an important source of water for all types of human uses, including drinking water, agricultural
and industrial uses.