Groundwater and Landscape Development
Water Below Earth’s Surface
Zone of Saturation is the portion of the ground
where all of the pore spaces are filled with
water.
Zone of Aeration is the portion of the ground
from the water table to the surface.
 pore spaces contain water and air
Capillarity is the ability of water to rise up in
small openings against the force of gravity.
Capillary Fringe is a narrow band just above
the zone of saturation where water can move up
against the force of gravity (capillary action).
Aquifer is a permeable layer of rock that holds
water and is sandwiched between two layers of
impermeable rock (see diagram below).
Aquiclude is an impermeable rock layer inside a
permeable rock layer (see diagram below).
Water Retention is the amount of water that
sticks to the outside of the particles of a porous
rock.
 Larger particles retain less water because
they have less surface area
 Smaller particles retain more water because
they have more surface area
Runoff is water flowing on the surface of the
Earth.
Runoff is affected by the following factors:
1. Saturated pore spaces in the ground cause
rainwater to flow on the surface because
water cannot infiltrate.
2. The amount of rain falling exceeding the
infiltration rate will cause runoff.
3. Runoff always occurs on impermeable
surfaces.
4.
A steep gradient will cause runoff.
5. Runoff decreases when vegetation covers
the soil.
6. Humans paving over the ground and
creating impermeable surfaces increase
runoff.
Runoff causes water to flow to streams directly
and not to infiltrate into the ground.
Streams carry the water directly to the oceans
and the aquifers are not recharged.
Most of our drinking water comes from the
groundwater that recharges our reservoirs.
Recharge is the addition of water to the soil
storage and aquifers under the surface.