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This 24" x 9" x 1/2" Plexiglas groundwater-flow
model can be built for $25 or less.
To learn more about the model, scroll through the present
To download plans and instructions for the model (gw_model.pdf),
click the button below.
To view photos of experiments, click any of the following
Other experiments will be added soon.
The groundwater flow model consists of the following
components and parts:
|| 24" x 9" x 1/4" Plexiglas
|| 40" x 5/8" OD vinyl tube with
12 small holes and 2 larger holes
|| water supply tube (1/4" ID vinyl tube,
1/4" OD plastic tube, 2 1/4" T's)
|| water discharge tube (1/4" ID vinyl
tube, 1/4" OD plastic tube, 1 1/4" T)
|| filter strips made of loose-weave fabric
|| #10 - 24 x 1 1/2" round-head machine
|| #10 - 24 wing nuts
|| 1/2" nylon spacers for #10 screws
|| #10 flat washers
|| extra vinyl tubing for various well configurations
|| small basting bulb for water extraction
Assemble the two Plexiglas sides of the model, as shown in
the exploded view, using the fastening hardware provided. This
will require the following:
|| #10 - 24 x 1 1/2 inch screws
|| #10 flat washers
|| 1/2 inch nylon spacers
|| #10 - 24 wing nuts
Only start the wing nuts onto the screws. Do not tighten them
at this point.
Slide the 5/8-inch (OD) vinyl tube into the top of the model,
as shown. Be sure that the 12 small holes (6 at each end) face
the center cavity of the model. Also, be sure that the 2 larger
holes face the outside of the model and lie below the 3rd screw
on each end.
Install the 14th fastening screw, with nylon spacer, 2 flat
washers, and a wing nut, in the center hole near the top edge
of the model.
Insert the water supply tube and the head adjustment tube
into the larger holes in the 5/8-inch vinyl tube.
Tighten all wing nuts, such that the 5/8-inch vinyl tube is
compressed between the Plexiglas sides of the model and forms
a water-tight seal.
Fasten the water supply tube and the water discharge tube
to the end of the model, as shown, using the 2 plastic ties.
Be sure that these tubes will slide through the ties, such that
the height of the head-controlling "T" is adjustable.
STEP 5 (not illustrated)
Carefully place fabric filter strips against the 5/8-inch
vinyl tube such that they cover the 12 small holes and hold strips
in place while filling the model with sand.
STEADY-STATE GROUNDWATER FLOW
The groundwater-flow model can be used to demonstrate
steady-state groundwater flow, driven by a constant hydraulic
gradient. In this case, a constant flow of water is supplied
through the water-supply tube. This is most simply achieved by
connecting the water-supply tube to a faucet and only slightly
opening the faucet valve. Once the model has filled with water,
water will begin to discharge through the water-discharge tube.
The desired hydraulic gradient (Dh/Dl) can
be achieved by careful adjustment of the faucet valve and the
height of head-controlling T's in the water-supply tube and the
water-discharge tube. The flow of supplied water should slightly
exceed that required by the model such that there is a constant
flow (drip) of excess water through the upper T in the water-supply
tube. This is illustrated below.
To demonstrate the down-gradient flow of groundwater,
inject dye-colored water to a position below the water table
through an injection well (illustrated). The resulting plume
will travel toward the discharge end of the model.
To demonstrate the problem of contamination in
flowing groundwater, extract water from a well positioned downstream
from the injection well. Ultimately, water from the colored plume
will be extracted.
To demonstrate how a water table is determined,
install 3 or 4 evenly spaced observation (piezometer) wells.
Water will rise in each well to precisely the height of the water
table at that position in the model.
PUMPING WATER FROM A WATER-TABLE AQUIFER, CONES
OF DEPRESSION, AND RELATED GROUNDWATER FLOW
Alternatively, the groundwater-flow model can be
used to demonstrate the effect on the water table of pumping
water from a well. In this case, the model is set up with a horizontal
water table, such that initially there is no hydraulic gradient.
To accomplish this, simply fill the model with water, pinch off
the water-supply tube, and adjust the head-controlling T's in
the water-supply tube and the water-discharge tube to the desired
level of the water table. This is illustrated below.
To demonstrate drawdown and the development
of a cone of depression extract water from a centrally
located pumping well. Observe the water levels in strategically
placed observation wells. Water levels will be drawn down in
observation wells, most significantly in observation wells closest
to the pumping well. A "cone of depression" is defined
by the drawn-down water levels.
To demonstrate that pumping water from a well induces
groundwater flow toward the pumping well, inject dye-colored
water into a well near the pumping well. The colored water will
stream toward the pumping well and will be drawn into the bottom
of the well if water is being extracted from it.