of Earth Science |Northeastern
Daily Objectives #15 (October
#2 will be held on Wednesday this week. For the exam, you should
be able to do the following:
v Define each of
v State the
hydrogeologic principles that
control or affect flow in each of the lab explorations:
table capillary zone
constant head boundary
hydraulic head pressure
v Describe the relationships
between and among the following properties
of porous materials:
porosity and effective porosity
specific retention and specific yield
specific yield and effective porosity
specific yield, specific retention, and porosity
hydraulic conductivity and intrinsic permeability
Give typical ranges of the
values of porosity, specific yield, and hydraulic conductivity of
different types of porous materials, using the correct units of
v List the kinds of rocks and
sediments that are generally considered
aquifers, and those that are generally considered aquitards.
v Sketch a cross section
illustrating the generalized hydrostratigraphy
of northeastern Illinois.
v Look at the map in the
Willman (1971) ISGS circular ("Summary of the Geology of the Chicago
Area"). Based on the information in the map/document, decide
where in the Chicago area people could find abundant ground water that
they could tap with wells that tap the sediment layer.
Then, combining this
information with the information on the map of the bedrock geology of
Illinois, identify areas that are likely to have abundant ground water
that can be tapped with wells that tap the bedrock.
On the NEIU campus, to find
water, would we need to drill wells
that tap the sediment layer, or the bedrock?
v Use your knowledge of
hydraulic properties to solve practical problems:
q Given a certain volume of
material and a description of the sediment type, estimate how much
water it would take to saturate it. Then estimate how much water
would drain from it, under the force of gravity.
q Figure out
water was lost from an aquifer during a drought (Chapter 3, Problem #9,
on p. 111).
v Tell what causes
ground water to flow in an aquifer.
v From memory, state Darcy's Law.
v Sketch the Darcy tube
apparatus and describe how it works.
Use Darcy tube experimental data to find hydraulic conductivity (K) of
sediment in the tube. Given values for some of the
variables, calculate the others. For example, given the K value of the sediment,
estimate the discharge (Q) that would flow through the tube under a
given gradient; or, given K and Q, estimate the gradient (dh/dl).
v Explain why it is important in the
Darcy tube experiment to keep a constant head in the inflow funnel.
In the ground water model, find
flow paths and hydraulic gradients data
from the piezometers only!
v Based on hydraulic head measurements from the
piezometers in the ground water flow model, draw a "map" showing flow
through the model. Include the following features:
flow lines showing the direction of flow (put an arrow on the end of
each flow line to tell the direction), contour lines that connect
points of equal hydraulic head, and boundaries to the ground water flow
v List the three different types of boundaries
to a flow system, and tell how flow lines in a "map" of ground water
flow directions are related to each type of boundary.
Demonstrate your understanding of each of the following:
head (h): Write a definition of hydraulic head,
tell how it is measured in the lab or field.
piezometer: Point to a piezometer on the Darcy tube,
point to a piezometer on the ground water flow model, find a water
level on a piezometer in the ground water flow model, explain to a
classmate what the purpose of a piezometer is, and use a piezometer on
the ground water flow model to measure hydraulic head at a given point
in the system as you explain to a classmate what you are doing.
Use hydraulic head measurements that you took last class period from
two piezometers to determine the hydraulic gradient in the Darcy tube,
explain how the hydraulic gradient is represented in the Darcy's Law
equation, point out an area of relatively high gradient on your flow
map from the ground water flow model, and point out an area of
relatively low gradient. Tell how your Darcy tube experimental
results would have been different if the hydraulic gradient had been
higher, and give two ways that you could set up the Darcy tube in such
a way as to increase the gradient.
conductivity (K): Explain the meaning of hydraulic
conductivity. Tell how your Darcy tube experimental results would
have been different if the tube had been packed with sediment having a
lower hydraulic conductivity.
head: Explain what is meant by the term constant
head. Explain how head in the Darcy tube experiment was kept
constant during the test. Point to a boundary on your map from
the ground water flow model along which the hydraulic head is constant.
Explain what is meant by the term discharge, and tell how discharge is
represented in the Darcy's Law equation. Give three ways you
could have reduced the discharge in your Darcy tube experiment without altering the construction of the
tube itself. Give two ways you
could have reduced the
discharge in your Darcy tube experiment by altering the construction of the tube
v Sketch a cross sectional view of three piezometers that
tap an aquifer at different depths, but with their openings in a
vertical line. Sketch the relative positions of water levels in
the three piezometers in four situations: Water in the aquifer at that
location is A) flowing downward, B) flowing upward,
C) flowing laterally (horizontally), and D) not flowing.
v Next up: Using data from
draw a ground water flow map, showing where the water table is.
of Earth Science | Northeastern
© 2005 Laura L.
Last updated October 24, 2005.