Hydrogeology and Groundwater Quality of Highlands ... - USGS

The principal source of groundwater supply in Highlands
County is the Upper Floridan aquifer. As of 2005, about 89
percent of the groundwater withdrawn from the county was
obtained from this aquifer. The surficial aquifer was the source
for about 9 percent of groundwater (M. Beach, Southwest
Florida Water Management District, written commun., 2009).
Most of the water from the surficial aquifer is obtained from
wells along the Lake Wales Ridge. The intermediate aquifer
system is only a minor source of water supply, contributing
about 2 percent of the total groundwater withdrawn
(M. Beach, Southwest Florida Water Management District,
written commun., 2009).
Although poorly documented, little groundwater is
withdrawn from the Lower Floridan aquifer for water supply
in Highlands County. In the northern part of the county
where the top of this aquifer is closer to land surface, some
wells may be open to both the Upper Floridan and Lower
Floridan aquifers to increase well yields. In much of the
county, however, the increased mineralization of water from
the Lower Floridan aquifer has prevented it from becoming a
source of water supply.
Moderate amounts of water are being withdrawn from
surface-water sources, which are primarily used for agricultural
irrigation. Surface-water withdrawals in the study area
are largely from a network of canals augmented by groundwater
and rainfall. Of the 153.93 Mgal/d of surface water
withdrawn in 1975, 58.7 Mgal/d was used for agricultural
irrigation with most of the remainder used for power generation.
In 2005, a total of only 11.45 Mgal/d of surface water
was withdrawn, of which 10.94 Mgal/d was used for agricultural
irrigation (Marella, 2009).
RECREATIONAL
IRRIGATION
2 %
HIGHLANDS COUNTY
107 million gallons per day
DOMESTIC
1 %
PUBLIC
SUPPLY
8 %
THERMOELECTRIC and
COMMERCIAL / INDUSTRIAL
less than 0.1 %
AGRICULTURE
89 %
Methods of Data Evaluation and Collection 13
Methods of Data Evaluation
and Collection
This section describes the types of well records and the
site numbering used in this report. In addition, the collection
and analyses of geologic and geophysical-log, water-level,
and water-quality data are discussed. Finally, the collection of
quality-assurance samples is described.
A network of monitoring wells was established for the
collection of groundwater samples from the surficial aquifer,
intermediate aquifer system/intermediate confining unit, and
Upper Floridan aquifer. Data-collection sites were inventoried
based on a review of wells and available water-quality data in
the study area. Additional wells added to the inventory were
obtained from well permits, well construction reports, and the
files of the USGS. The locations of wells used for data collection,
including wells used for the collection of water-quality
data, are shown in figure 11.
Well Records and Site Identification
Well records in Highlands County are maintained by
several government agencies. The USGS, SWFWMD, and
SFWMD have computerized databases and paper files on
wells that contain water-quality, water-level, geologic, hydrologic,
geophysical-log, and water-use data. The USGS assigns
a unique 15-digit number based on latitude and longitude that
is used to identify wells in the USGS National Water Data
Information System (NWIS). The first six digits denote the
degrees, minutes, and seconds of latitude; the next seven digits
denote degrees (using three digits beginning with 0), minutes,
and seconds of longitude; and the last two digits denote a
sequential number to identify wells within a 1-second grid.
For example, well 271114081122401 is the first well inventoried
at latitude 27° 11′ 14″ N, longitude 081° 12′ 24″ W. Once
assigned, a site identification number does not change even
though the locations determined by latitude and longitude may
be revised later.
The FGS keeps records of geologic data throughout the
State, including more than 100 wells in Highlands County.
Well data from the files of the FGS are identified using their
“W” prefix followed by a number.
Information from selected wells used in this study is
given in appendix 1. Wells included are completed in the
surficial aquifer, intermediate aquifer system/intermediate
confining unit, and Floridan aquifer system. Included in this
appendix are the types of data collected during this study, well
construction data, and general information about the wells.
A map reference well number up to three digits is used to
identify wells throughout this report.
Figure 10. Total groundwater use, by category, for 2005.
From Marella (2009).