Caribbean-Florida Water Science Center
Lake Wales Ridge Groundwater Study
The groundwater study is focused on the unconfined surficial aquifer. The Ridge monitoring network currently includes 30 wells (“citrus land-use network”), which were surrounded by active citrus groves (orchards) at the time the study was initiated in 1999, and 8 wells in non-citrus land-use consisting of residential and commercial areas and pastureland. At some of the citrus-network well sites, during the course of the study, land-use has been converted from citrus to residential development. Further details describing the design and implementation of the citrus land-use monitoring network are described in Choquette and Sepulveda, 2000.
The citrus land-use network was established in three phases (see map). Well sites were selected using a grid-based sampling approach focused on areas of the Ridge in citrus agriculture and on soils classified as vulnerable to agrichemical leaching. The “vulnerable soils” correspond to NRCS (Natural Resources Conservation Service, U.S. Department of Agriculture) soil map-units characterized by high permeability and low organic-matter content (see Choquette and Sepulveda, 2000).
The sampling history (Excel file) at the Ridge network wells spans the period 1989 to present, and is ongoing (as of 2011). The Phase I of the Ridge citrus network includes a subset of wells that were sampled between 1989 and 1999, previous to this study, as part of the Florida Department of Environmental Protection “Background” and “VISA citrus” monitoring networks, and by the U.S. Geological Survey (German and others (PDF), 1996). Sampling frequency of the Ridge citrus-network wells was intermittent from 1989 to1999 (for a subset of wells), quarterly from 1999 to October 2009, and semi-annually from October 2009 to present. During 2009, eight wells in non-citrus land-use areas were added to the network, and were sampled in January and July 2009.
Groundwater sampling is performed by the Southwest Florida Water Management District and Florida Department of Agriculture and Consumer Services staff. Groundwater samples are collected and processed according to Florida Department of Environmental Protection groundwater sampling protocols which are consistent with U.S. Geological Survey protocols (PDF) with the exception that filtering of samples for pesticide analysis is limited to selected analytes. Field protocols include a minimum purge of three well volumes, and stabilization of pH, conductance, temperature, and dissolved oxygen (measured continuously) prior to sample collection. Quality control and assurance samples represent at least 25 percent of collected samples.