2. Groundwater occupies pores or open space within Earth materials
Porosity = measure of the % of total volume
of a material occupied by open space (pores)
Depends on (for example):
abundance and distribution of fractures
shape and size of openings
in sediments, packing of grains, cementation, etc.

3. Low Porosity < 5 % High Porosity > 15 % Mud
Unconsolidated sediment
20 to 50 %
Mud
high porosity
Low Porosity
< 5 %
High Porosity
> 15 %
Figure 19.2

4. Permeability = ability to transmit fluids
Depends on:
total porosity
interconnections between openings
Figure 19.4

5. Water Table Contact between unsaturated and saturated
Figure 19.6
Capillary Fringe- water lifted up
by tension against pull of gravity

6. can be some distance from the surface 100 to 200 m
Figure 19.6
Water saturated
Water saturated
Arid region
can be some distance from
the surface
100 to 200 m
lakes and rivers provide
water to the ground
Humid region
groundwater
can be very near the surface
lakes and rivers directly
connected to the

7. Gravity drives the flow of groundwater
moves to lower elevation along curved paths
Figure 19.9

10. Hydraulic head – elevation and pressure
at the water table pressure = 0
so hydraulic head = elevation or slope of the water table
Figure 19.11