Measuring Water Levels in a Flowing Well

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Detailed Description

This video demonstrates how to measure low pressure hydraulic head in a flowing well.

Details

Image Dimensions: 480 x 360

Date Taken:

Length: 00:04:04

Location Taken: Tucson, AZ, US

Transcript

Introduction
Hi, I’m Jesse Dickinson, a hydrologist with

the US Geological Survey.

We’re here in the San Pedro Basin in Southeastern
Arizona, and we’re going to demonstrate

how to measure hydraulic head in an artesian
well.

Materials:
The materials needed include:

A pipe wrench, A plug for the well, A clear
plastic column that can be attached vertically

to the opening of the well , Plumbers tape
to ensure a tight fit to the well and to minimize

leaking, A pencil or pen if using a water
level field form, or a device for electronic

data entry, A ruler or tape for measuring
the height of water in the plastic tube, A

level to ensure that the ruler or tape is
perpendicular to the land surface

Instructions:
Step 1) Determine you are at the correct well

from the well description and locate the documented
measuring point(s) and land surface datum

from well photo or diagram.

Step 2) If necessary, use a pipe wrench or
other tool to remove any plugs in order to

gain access to the well.

Step 3) Apply plumbers tape to ensure a tight
fit between the well opening and the plastic

pipe to minimize leaking.

Step 4) Connect a length of transparent plastic
pipe tightly to the well.

Step 5) Gradually close any other opening
to the flowing well.

If pressure is applied suddenly, the well
could be permanently damaged by the “water-hammer

effect” by caving of the aquifer material,
breakage of the well casing, or damage to

the distribution lines or gauges.

Step 6) Ensure that all flow from the well
stops so that a static water-level measurement

can be made.

Step 7) Rest the ruler or measuring tape on
the measuring point (MP) and use the level

to check that the ruler or tape is perpendicular
to the land surface.

Use the scale to read the height above the
measuring point that the water has risen in

the plastic pipe.

Step 8) Record the date and time of the measurement
on a Water Level Measurement Field Form or

a digital screen input form.

Because the water level is above the measuring
point, this is a negative number.

Step 9) Record the measuring point (MP) correction
length on the “MP correction” row of the

field form or select the MP used from the
electronic data entry form.

Subtract the MP correction length from the
true “water level below measuring point”

value to get the depth to water above the
land surface datum as a negative number.

The MP correction is positive if the MP is
above the land surface, or negative if it

is below the land surface.

On the field form, record the water level
in the “WL below LSD” column.

Step 10) Make a check measurement by performing
the previous steps.

Record the check measurement on the field
form or electronic data entry form.

If the check measurement differs from the
original measurement by greater than 0.1 or

0.2 foot, continue to measure the water height
until the reason for a lack of agreement is

determined or the results are found to be
reliable.

Complete the “final measurement for GWSI”
portion of the paper or digital field form.

Step 11) Gradually remove any plugs to the
flowing well.

If pressure is applied or released suddenly,
the well could be damaged.

Step 12) Remove the clear plastic pipe from
the opening of the well.

Step 13) Attach any other plugs to well openings.

Limitations:
Keep in mind the following limitations of

this method.

Low-pressure head measurements are most feasible
when the head is less than six feet above

the land surface.

Measurements are commonly accurate to 1/10th
of a foot.

All flow from the well should be shut down
so that a static water level measurement can

be made.

However, the time required to reach a static
pressure after flow discontinues may range

from hours to days.

Since a true static measurement may be impractical,
record the time after shutting off the flow

for each measurement.

Advantages:
An advantage of a method for low pressure

measurement is that it is generally simpler,
faster, safer, and more accurate than a method

for high pressure measurement.

Disadvantages:
A disadvantage is that this method may be

impractical for wells with heads greater than
5 to 6ft above the land surface.