Group Title: Citrus Station mimeo report - Florida Citrus Experiment Station ; CES 66-5
Title: Problems encountered with water table observation wells
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 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
Subject: Irrigation -- Florida   ( lcsh )
Water-supply engineering -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
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


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

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