GeoLab 11
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University of Dayton *
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SCI-210
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Geography
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Dec 6, 2023
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GEO 109L – Earth, Environment, & Society Lab
Lab Exercise 11 – Groundwater
Introduction
Next to the oceans and ice caps, groundwater is the
largest water reservoir on Earth. We rely on our
groundwater resources for individual water access as
well as municipal, industrial, and agricultural water
supply on a large scale.
Because of the constant and
increasing demands, it is essential for individuals and
local, state, and federal agencies to work to maintain the
quantity and quality of this resource.
In this week’s lab
we will investigate both the nature of the materials that
groundwater moves through as well as how exactly we
study this part of the hydrologic cycle that we cannot
readily observe (it is underground)!
Materials:
Flow Test Materials
Stopwatch
Ruler
Calculator
Pencil
Lab Exercise
Part 1 – Flow Test
In order for scientists and water engineers to understand the speed at which groundwater moves through an aquifer,
which ultimately affects the rate at which water can be pumped out and how fast potential contaminates move from
a source to other areas of the aquifer, they first must perform tests on well bore samples from the aquifer. These
tests, referred to as flow tests, send a certain amount of water through a sample under a set pressure in order to
observe how much water can be stored in the material and how fast it moves entirely through the sample.
We will recreate a portion of this type of test today in lab.
We are going to simplify the test and use open
funnels under the force of gravity to drive our flow test.
Follow the procedure (green box) and then answer the
questions following.
Your flow test set up is already set up in the center of your table. You have three sediment (unconsolidated or loose)
types. Each funnel holds approximately 100 cm
3
of sediment.
You also have a 250 ml beaker with 100 ml of water in
it and an empty 100 ml beaker or 250ml beaker with graduated cylinder.
Place the empty 100 ml beaker (or 250 ml beaker) under one of your funnels.
You will complete three flow tests, one at a time.
DO NOT START THE FLOW TEST UNTIL YOUR TIMER IS
READY
.
You will be recording multiple time points during the test. The time it takes for the first water to leave the
funnel AND how long it takes until water stops leaving the funnel (all/most of the water has moved through
the sample).
Once the timer is ready, start timing and pour the 100 ml of water into the funnel (if the water nears the lip
of your funnel, wait until the water level drops to finish adding all the water).
Record your times in the table following
. IF YOUR WATER TAKES LONGER THAN 2 MINUTES
to move
through your sample. Stop your test at 2 minutes and record how much water moved through during that
time.
Lab 11 | 1
NAME: ____________________
Table # ___
1)
RECORD YOUR FLOW TEST RESULTS BELOW
2)
Rank your three sediments below in order of highest (a) to lowest (c) permeability.
a)
b)
c)
3)
In the table below, write next to each K value (hydraulic conductivity) which sediment type you think best
fits.
4)
Below is a cross-section (side view) of the Great Miami Buried Valley Aquifer (GMBVA). Dayton and most of
Southwest Ohio relies on the GMBVA for the majority of our water needs.
This aquifer is composed of a pre-
existing (pre-Ice Age) bedrock valley that was filled with loose sediment as the Ice Age glaciers advanced and
retreated over 500,000 years. The sediments include Sand, Gravel, and Clay.
Determine which of the
sediments of the GMBVA are an
AQUIFER
layer or a
CONFINING
layer.
Sand and Gravel:
______________
Clay: ______________
2
Sediment Type
Time Water First Leaves
Funnel (secs)
Time Last Water
Leaves Funnel (secs)
Amount of Water After
2 minutes (ml)
Fine Sand
Gravel
Clay
Sediment Type
K value
gravel
1,000 ft/day
Fine sand
100 ft/day
clay
1 ft/day
Part 2 – Groundwater Table Map: Contouring, Flow, and Velocity
For the rest of the lab you will complete a groundwater system problem similar to what you completed for your
prelab. The map (see last page of lab) will be slightly more complex, but the skills and calculations will all be the
same as the contour map you made in Lab 8.
Your instructor will provide a hard copy of the map for you to draw
on.
5)
Contour the map provided for a representative area within a groundwater system similar to the GMBVA.
The labeled dots are groundwater table elevations in feet. Make sure to use a
contour interval of 2 ft.
NOTE:
– Contour line for 568 feet is drawn in for you.
This will help to show you the pattern for all
the contour lines across the map.
6)
Draw in groundwater flow lines starting from each of the orange, lettered industrial building sites. Feel free
to add more lines if you would like.
NOTE:
Each person’s contour and flow lines may vary slightly, BUT still be correct.
7)
Which of the industrial sites (letters) could contaminate the well field?
Letter C
8)
Which of the industrial sites (letters) could contaminate the wetland?
Letter D
9)
What is the hydraulic gradient between site C and the well field? Show your work.
.004
10)
Using Darcy’s Law and a K value of 500 ft/day and porosity of 30%, how fast would the groundwater be
moving (velocity) between site C and the well field? Show your work.
6.7 ft/day
11)
How long would it take contamination to reach the well field from site C? Show your work.
About 1 ½ days
12)
What is the hydraulic gradient between site D and the wetlands? Show your work.
Hg=.002
13)
Using Darcy’s law and a K value of 400 ft/day and a porosity of 25%, how fast would the groundwater move
between site D and the wetlands? Show your work.
3.2 ft/day
Lab 11 | 3
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