This document provides an overview of groundwater, including: - Groundwater is found underground in the spaces between sediment and cracks within rock. It is recharged through precipitation and snowmelt infiltrating the ground or, in some cases, streams. - Aquifers are underground layers that can store and transmit water. They can be confined, with impermeable layers above and below, or unconfined with no upper boundary. - Groundwater is discharged through pumping wells, which cause drawdown, or into surface water features like streams, wetlands, and lakes.

1. Earth’s Environment
Lecture Outline : Groundwater

2. Where is the water on Earth?
Look at the next slide’s diagram. In it
you’ll see that most of the water on Earth
is salt water. Out of the fresh water, most
is frozen. Groundwater makes up the
largest portion of fresh, liquid water on
Earth.

4. Where is groundwater and how
does it get there?
The Water Cycle shows us how water
moves from phase to phase (gas, liquid
and solid) and from place to place on
Earth.
Water that infiltrates into the earth
becomes groundwater.

6. Where do you find
groundwater?
Groundwater can be found in between
individual pieces of sediment in a layer of
unconsolidated material (not solid rock,
but layers of sand, gravel, silt, etc.)
Groundwater can also be found in the
spaces that exist within solid rock.
– Either pore spaces between individual grains
– Or in cracks that exist in solid rock

7. Intergranular = pore spaces in solid rock
or unconsolidated material
Fractured bedrock = cracks in solid rock
Solution enhanced = cracks that have
been enlarged by groundwater dissolving
rock

8. Types of Aquifers
An aquifer is a layer of sediment or rock
capable of holding and transmitting
significant quantities of water.
Aquifers that have an impermeable layer
above and below them are called
“confined aquifers”
What’s an impermeable layer? A layer of
rock or sediment that doesn’t allow water
to flow through easily.

9. Unconfined aquifer
Also called a “Water Table” aquifer, this
type does not have an impermeable layer
above the aquifer.
See the next slide for a diagram showing
two confined aquifers and one unconfined
aquifer.

10. The Confining beds are also called
aquitards. They retard, or slow, the flow of
water.

11. Other terms
The water table is the top of the saturated
zone.
The saturated zone is the layer in the
aquifer where every pore space or every
crack is completely filled with water
The unsaturated zone exists above the
saturated zone, and may have moisture,
but the pore spaces or cracks also contain
air.

12. Vadose zone and zone of aeration are
other words for the unsaturated zone.
Water from the saturated zone can move
upward through capillary action into the
unsaturated zone.

14. Water table divides the two zones. The
position of the water table will vary. More
recharge raises the water table.

15. Source of water – Unconfined
In an unconfined aquifer, water will seep into
the ground directly above the aquifer. This is
the recharge area.

16. Source of water - Confined
In a confined aquifer, the overlying aquitard
prevents water from the surface from
seeping into the aquifer.
Recharge, therefore, often comes from far
away, in a place where the aquifer meets up
with the surface.
See the illustration on the next page.

18. GROUNDWATER RECHARGE

19. Groundwater entering the
ground = RECHARGE
Recharge comes from direct precipitation
Or snow melt
Or, in certain situations, it can come from
a stream

20. Precipitation

21. Streams as a source of groundwater
recharge (mostly in dry climates)
In locations where the
water table is below
the bottom of the
stream, water from the
stream can run into the
ground and feed the
groundwater.
This is called a losing
stream or an influent
stream.

22. Induced recharge into wells
from streams
There are some situations where, even in
humid climates, water from streams ends
up in wells. This occurs when a pumping
well is located in an aquifer near a river.
Water from the river is pulled into the
pumping well. These tend to be very
productive wells – there’s a constant
source of water. However, it is river water,
albeit, filtered through the ground, but
there can be quality issues.

23. Streams feeding groundwater through “Induced Recharge”

24. GROUNDWATER DISCHARGE

25. Groundwater Discharge
Groundwater can be discharged from the
aquifer either through a
– Pumping well
– Or a stream

26. Pumping wells lower the groundwater
through “drawdown”
Drawdown often forms a cone-shaped
depression around the well, called a “cone
of depression.”

27. Groundwater is also discharged
into surface streams, wetlands
and lakes (in humid climates).