Finals: Assignment # 1
Due: November 19, 2020
1. Identify and define/explain at least 20 important terms that you can find in Lesson # 1.
๏ The unsaturated zone or vadose zone extends above the water table and includes the
soil water zone down to the water table, which divides the unsaturated zone from the
saturated zone.
๏ The water table is defined as the level to which water will rise in a well drilled into the
saturated zone.
๏ The soil water zone, which extends from the ground surface down through the major
root zone, varies with soil type and vegetation. The amount of water present in the soil
water zone depends primarily on recent exposure to rainfall and infiltration.
๏ Hygroscopic water remains adsorbed to the surface of soil grains.
๏ Gravitational water drains through the soil under the influence of gravity.
๏ Capillary water is held in the zone just above the water table and exists because water
can be pulled upward from the water table by surface tension.
๏ The capillary zone, or fringe, extends from the water table up to the limit of capillary
rise, which varies inversely with the pore size of the soil and directly with the surface
tension.
๏ Capillary rise can range from a few cm for fine gravel to more than 200 cm for silt
(Todd and Mays, 2005).
๏ In the saturated zone, which occurs beneath the water table, the porosity is a direct
measure of the water contained per unit volume, expressed as the ratio of the volume of
voids to the total volume.
๏ Specific yield is defined as the volume of water released from an unconfined aquifer per
unit surface area per unit head decline in the water table.
๏ A well is a vertical hole dug into the earth, usually cased with metal or PVC plastic up to
the land surface.
๏ The portion of the well hole that is open to the aquifer is screened to prevent aquifer
material from entering the well.
๏ A vertical penetration used to collect soil or water samples that is not cased is called a
borehole.
๏ An aquifer can be defined as a formation that contains sufficient permeable material to
yield significant quantities of water to wells and springs. Aquifers are generally areally
extensive and may be overlain or underlain by confining beds. Most aquifers can be
considered underground storage reservoirs that receive recharge from rainfall or from an
artificial source. Water flows out of an aquifer due to gravity or to pumping from wells.
๏ An aquiclude is saturated and is a relatively impermeable confining unit, such as clay,
that might act as a confining layer above or below an aquifer system.
๏ An aquitard is a saturated, low permeability stratum, such as a silty clay, that may leak
water from one aquifer to another.
๏ Aquifers may be classified as unconfined, depending on the existence of a water table,
defined by levels in shallow wells.
๏ A confined aquifer is one that is overlain by a confining unit and is under pressure.
๏ A leaky confined aquifer represents a stratum that allows water to flow from above
through the confining zone.
๏ A perched water table is an example where an unconfined water body sits on top of a
clay lens, separated from the main aquifer below.
