Groundwater and Freshwater Sources

Study Notes

Groundwater, or water below the surface, makes up most of Earth's liquid freshwater.
Only about 1% of Earth's liquid freshwater is above ground, in streams, lakes, rivers, and ponds.
Groundwater gets underground when rain or snow seeps into the ground, and the type of soil affects how well it absorbs water (e.g., sand is good, clay is poor, rocks are worse).
The saturated zone is where groundwater completely fills underground spaces, while the unsaturated zone has moisture but doesn't fill all spaces.

The water table is the boundary between the saturated and unsaturated zones, visible when digging a hole and seeing water fill the bottom.

Groundwater is crucial in the water cycle, feeding rivers, lakes, streams, and oceans.
Aquifers, like the Ogallala Aquifer, store massive amounts of groundwater, taking thousands to millions of years to fill.
Groundwater acts as a cementing agent, helping form sedimentary rocks by carrying and gluing sediments together.

Geysers form when groundwater above a near-surface magma source heats up, building pressure and eventually escaping as steam.
Groundwater supports natural ecosystems, providing freshwater for surface water systems, and is essential for plants and animals.

We pump groundwater for drinking, irrigation, and other uses, but this can lead to problems, as aquifers take a long time to refill.
Over-pumping can cause land to sink, creating sinkholes, and dissolves rock to create caves.