Full Citation |
Material Information |
|
Title: |
Problems encountered with water table observation wells |
|
Series Title: |
Citrus Station mimeo report |
|
Physical Description: |
2 leaves : ; 28 cm. |
|
Language: |
English |
|
Creator: |
Ford, Harry W., 1922- Citrus Experiment Station (Lake Alfred, Fla.) |
|
Publisher: |
Citrus Experiment Station |
|
Place of Publication: |
Lake Alfred FL |
|
Publication Date: |
1965 |
Subjects |
|
Subject: |
Irrigation -- Florida ( lcsh ) Water-supply engineering -- Florida ( lcsh ) |
|
Genre: |
government publication (state, provincial, terriorial, dependent) ( marcgt ) non-fiction ( marcgt ) |
Notes |
|
Statement of Responsibility: |
Harry W. Ford. |
|
General Note: |
Caption title. |
|
General Note: |
"October 13, 1965." |
Record Information |
|
Bibliographic ID: |
UF00072437 |
|
Volume ID: |
VID00001 |
|
Source Institution: |
University of Florida |
|
Rights Management: |
All rights reserved by the source institution and holding location. |
|
Resource Identifier: |
oclc - 76759007 |
|
Full Text |
CES ^(*-*)
Citrus Station Mimeo Report CES 66-5
October 13, 1965
PROBLEMS ENCOUNTERED WITH WATER TABLE OBSERVATION WELLS
Harry W. Ford
Citrus Experiment Station
Lake Alfred, Florida
Most of the water table observation wells installed for grower use
have consisted of either 4 inch or 6 inch irrigation or fiber pipes. It
has usually been recommended that holes be drilled in the pipes to equalize the
water level. In sandy soils, the holes have been small to prevent silting
of the pipes. Some wells have been installed without holes. It has usually
been assumed that water levels would be the same with or without holes.
Piezometric pressure measurements now indicate that open water table
observation wells installed in certain locations are not giving a true
indication of the water table. The cause of the trouble has been high
pressures in certain aquifers (usually marl sandwiched between two clay
layers) in which the water has been under rather high pressure. The pres-
sures result in abnormally high water levels in 'the open water table wells
following certain rainy conditions. The water in the wells may also re-
cede at a more rapid rate than the actual water table in the soil.
It is suggested that you perform certain tests if you are using water
observation wells with small holes or no holes and where the pipes extend
into clay or through clay into marl. After heavy rains when the water
observation wells indicate levels within 18 inches to 24 inches of the
surface, auger a hole adjacent to the observation well and note the level
of the water that stabilizes in the auger hole. This may take 15 minutes
to one hour. You can be suspicious of complications from subsoil hydro-
static pressures if the water level in the pipe is higher or lower than the
water table in your auger hole. It is essential that you do not dig the
auger hole into the clay or marl.
I would like to emphasize that the hydrostatic pressures encountered
have not been found in all sites containing marl. They exist only where
there is a relatively porous aquifer sandwiched between two layers of
somewhat impermeable material.
It is suggested that all water table observation wells be installed
to a depth of no more than 4 feet. Holes should be drilled in the pipes
to equalize pressure. The holes should be at leat 3/8 inch in diameter
to minimize plugging from iron oxide caused by the action of certain bac-
teria. The pipes must be surrounded with gravel, sawdust or other filter
material that will prevent sand from flowing into the pipes. It is also
desirable that all of the pipes be installed at known heights aboveground
and at known elevations'to obtain the maximuminformatibnabout the water
table in relation to ditches or tile lines.
Citrus Experiment Station
Lake Alfred, Florida
150-10/13/66 HWF
|
|