South Carolina Department of Environmental Services
Link to: South Carolina Department of Environmental Services Groundwater Information
NGWMN Contact:
Brooke Czwartacki
(843) 619-1950
The South Carolina Department of Environmental Services (SCDES) is a water-level data provider to the National Groundwater Monitoring Network (NGWMN). SCDES maintains a database of 14,146 wells, including some that have over 50 years worth records. Majority of wells managed by SCDES are equipped with automated data recorders (ADRs), which measure and record water levels every hour. SCDES currently serves data from 397 sites to the NGWMN Portal. SCDES has been a part of the Network since 2015.
SCDES provides water-level data from the Surficial aquifer system, the Floridan aquifer system, the Southeastern Coastal Plain aquifer system, and the Piedmont and Blue-Ridge crystalline rock aquifers
NGWMN Projects:
Initial Project to become a NGWMN data provider.
2016 Round 2: 10/1/2016 to 5/1/2018
Project is to fill site information data gaps. The first part of the work involves entering lithologic data, well-construction data, and historic water-level data at NGWMN sites. The second part of the work is to determine tidal corrections for thirty network surveillance monitoring wells completed in the Upper Floridan aquifer. Five pressure transducers will be installed on rotating short-term deployments to collect the water-level data needed for the corrections.
Project is to provide persistent data services, do site-information gap drilling, and drill a replacement NGMWN well. The work for persistent data services is for two years. Work under site information gap filling consists of 3 parts. Lithologic and well construction information will be entered from paper files, historic continuous water-level data will be entered into new database so that it is available to the NGWMN, and a GPS survey will be conducted at 63 wells to get more accurate locations and altitudes. The final part of the project is drilling a replacement well in the Columbia Plateau basaltic-rock aquifer. The new installation will have wells at 300, 600, and 900 feet.
Project is to do well maintenance activities and to drill two new wells to fill NGWMN gaps. Well maintenance work involves well-head repairs to 15 wells to secure the wells and pumping 4 monitoring wells to verify connection to the aquifer. Well drilling work is to construct two additional wells at new major aquifers to an existing site in Richland County.
This project is to pump seven wells to clear screens and maintain connection to the aquifer and to purchase continuous water-level monitoring equipment to replace aging equipment.
NGWMN Presentations:
December 2016 presentation to SOGW
Site Selection and Classification
Site Selection
Based on the Guidance provided by the NGWMN, sites were selected from both the DNR Groundwater Monitoring Network and the Potentiometric Mapping Well Networks. Sites were selected based on their period of record, anticipated future monitoring, spatial distribution and value to answering trans-boundary issues. After sorting sites based on period of record and anticipated future availability of the monitoring sites, wells were evaluated for inclusion or exclusion in the NGWMN by a committee of hydrologist from DNR. Sites from the Groundwater Monitoring Network are considered "Trend" sites for the frequency of data collection. "Surveillance" sites were selected from wells in the Potentiometric Mapping Well Networks. The resulting selection identified 137 Trend and 301 Surveillance wells for inclusion into the NGWMN.
Site Classification
Using the guidance provided from the NGWMN, the wells selected for inclusion in the National network were classified into subnetworks. A committee of hydrologists from DNR examined the data available for each well. Hydrographs were created and examined to identify wells that had documented anthropogenic changes. Potentiometric maps were used to identify wells that are located within a documented cone of depression. Additionally, water-use data collected from DHEC was examined to identify wells where changes in water levels may be anticipated.
Wells located away from areas of high reported water use and where no documented declines in water levels were observed, were assigned to the "Background" subnetwork. Wells that had data suggesting anthropogenic impacts or in areas of high water demand were assigned to the "Suspected/Anticipated Changes" subnetwork. Wells with documented declines or wells that were located within cones of depression identified by potentiometric mapping were assigned to the "Documented Changes" Subnetwork.
Data Collection Techniques
Site Visits
All SCDES monitoring network sites classified as Trend Sites in the NGWMN are currently visited at least six times per year. During each site visit and for every well, a manual water-level measurement is taken from the designated measuring point and recorded in a field book along with the date and time of the measurement. For wells equipped with ADRs (Automatic Data Recorders), current or real-time readings are obtained from the ADRs (for both water-level sensors and barometric sensors, if applicable) and recorded in a field book. Data are downloaded from the ADRs and evaluated on site to check instrument performance. For pressure transducers, the sum of the sensor's current water-level reading (height of water above probe, corrected for barometric pressure, if applicable) and corresponding manual measurement (depth to water) is calculated during each site visit. This sum, called the cable length, should be the same value for each site visit.
Comparing cable length values from consecutive site visits is a means of assessing transducer performance. A minor change in cable length (0.2 ft or less for most transducers) indicates that a potential instrument fault may exist, but the ADR is not typically replaced. When cable-length tolerances are exceeded repeatedly after additional site visits, either the ADR is recalibrated, or an instrument failure is confirmed, in which case the transducer is replaced and the associated records are not added to the groundwater database. For newer transducers, the cable-length variations observed between consecutive site visits typically have been less than 0.10 ft. Site maintenance includes replacing saturated desiccant packs at sites equipped with vented transducers; the desiccant prevents the buildup of moisture in the transducer's vent tube, which can cause faulty water-level readings and damage the equipment. Other maintenance procedures include checking for battery failure, communication errors, and spurious data spikes caused by lightning or other electromagnetic interference. Malfunctioning equipment, either ADRs or direct-read cables, are diagnosed and replaced or repaired as needed. Any issues with or changes to instrumentation are documented in a field book.
SCDES sites that are classified in the NGWMN as "Surveillance" sites are typically visited once every three years around November. These sites are manually measured using a variety of E-tapes, Steel Tapes and Pressure Gauges. Wells are required to be shut down and allowed to recover before measurements are taken. Measurements are recorded on field sheets provided by SCDES.
Automated Measurements
Two types of water-level sensors, shaft encoders and pressure transducers, historically have been used for automated monitoring stations whose readings are calibrated to manual measurements. By the summer of 2014, all shaft encoders were removed and replaced with pressure transducers. Shaft encoders measure depth to water and consist of a float, counterweight, cable, and pulley assembly. The float and counterweight hang freely inside the well, connected by a cable that runs over a pulley mounted near the top of the well. As the water level in the well changes, the float also moves, causing the pulley to rotate. The rotation of the pulley is measured optically or electronically, and that movement is translated into a measurement of the change in water level. Shaft encoders have a rated accuracy and resolution of 0.01 ft (feet).
Pressure transducers are installed in wells at fixed depths, below the expected range of water levels, and provide a measurement of the height of water above the sensor. The sensor contains a semiconductor strain gage: Changes in the height of water above the sensor changes the pressure on the sensor, which deforms the crystalline lattice of the sensor's silicon diaphragm, changing the sensor's electrical resistance (piezoresistive effect) to a constant input voltage, thus changing the output voltage. Water depth is computed from the output voltage measurement. Pressure transducers are deployed in wells using direct-read cables, which eliminates the need to remove the sensor from the well in order to download data. Most transducers in the network have a measurement range of 0-65 ft and an accuracy and resolution of less than 0.07 ft and 0.01 ft, respectively. Most transducers are not vented to the atmosphere and thus measure the combined pressure of both the water column and the atmosphere. Because unvented transducers require barometric compensation to remove the effect of atmospheric pressure, barometric data are collected at strategic sites throughout the State. Efforts are made to ensure that a barometric monitoring site is located within 20 miles of each unvented monitoring well. Vented transducers, which have sensors open to the atmosphere via a vent tube and thus require no barometric compensation, are installed in a few wells along the coast. Water-level and barometric transducers are synchronized with one another and record data every hour. Shaft encoders also recorded water levels every hour.
Manual Measurements
Manual water-level measurements or 'tape downs' are typically made using an electric tape, which consists of a pair of wires set inside an insulated sheath, the outside of which is marked like a measuring tape. The wires are attached to a steel probe at the bottom of the tape, but the design of the probe is such that there is a small gap between the two wires, keeping an electric circuit open. The tape is lowered into the well until the probe reaches water, which completes the electrical circuit and sounds a buzzer, indicating that the tape has reached water. The operator then reads the depth measurement on the tape, indicating depth of water from the measuring point. Where well construction will not allow for the use of an electric tape a steel tape may be used. At some sites, the groundwater is under enough pressure to cause the water level in a well to rise above the height of the well casing, and if the well were uncapped, water would flow freely from the well. Water levels in these flowing artesian wells cannot be measured using the typical tape-down procedure; instead, a pressure gage is attached to the well and the water pressure inside the well is measured. The water pressure is then used to calculate to what height the water would rise if the well casing were high enough to contain it.
A complete description of standard field operating procedures is included in Appendix B of the final report.
Data Management
Collected data is typically processed and further reviewed for quality assurance within one to two weeks after a site visit. All data that have passed quality assurance checks are entered into an Oracle database that uses Microsoft Access as a user interface. The instrumentation history of each well is documented in the database. Documentation includes the types and models of instruments deployed, dates of operation and performance history. In addition, the original field notes are kept and maintained for each well site, and copies are periodically produced in case field books are lost or damaged.
Data processing and storage for manual and automatically recorded data are as follows: Manual measurements, along with the date and time of the measurement, are entered into the Oracle database. These measurements indicate the depth to water from a specific measuring point on the well. The measuring point height (MPH) in feet above or below land surface for each well is stored in the database. An Access query is used to subtract the MPH from the raw manual measurement to compute a water level in feet below or above land surface. Changes in the MPH height, if any, are documented within the database. For ADR (Automatic Data Recorder) data, the logged hourly measurements are stored in both raw-data and processed-data files. The raw-data files contain uncorrected (uncompensated) hourly measurements and reflect the readings and the performance of various sensors as they were originally stored in data loggers. Raw data are stored mainly 'as is' and are archived at the SCDES for insight into hardware conditions and for quality assurance. Processed data files consist of hourly water-level data that have been corrected (compensated) for barometric pressure (unvented transducers only). Computer software, specific to each brand of instrument deployed, is used to generate barometrically compensated files, which are also archived at the SCDES. The software is also used to plot and review both the raw and compensated data at each ADR site as a final quality assurance check prior to entering the data in the database. When appropriate, data are winnowed of measurement anomalies and unreliable data thought to be the result of hardware failures. The real-time ADR reading (after barometric compensation, where applicable) is entered into the database and is used along with the corresponding manual measurement to compute a cable length value. The computed cable length value is confirmed to be within the allowed tolerance before any hourly data are added to the database (typically +/- 0.20 ft). Logged hourly water-level measurements (after compensation, where appropriate) are imported into the Oracle database. These measurements reflect the height of the water column above the sensor and are permanently stored in the database. The well's MPH and the transducer's cable length value are used to convert the hourly readings to water levels in feet below or above land surface, which are also permanently stored in the database. Statistics Daily average water levels, in feet above or below land surface, are calculated from the hourly data for those days missing 7 or fewer hourly measurements. Monthly average water levels are calculated for each month having 5 or fewer days of missing record, while monthly high and low water-level values are recorded for each month having at least one day of data. Yearly averages are computed for each calendar year having 60 or fewer missing days of record, while yearly highs and lows are recorded for each year with at least one day of data. No statistics are calculated for wells that are manually measured owing to the relatively small number of data values available for such wells. Data collected from the network are available on the SCDES website.
Other Agency Information
Web sites of Interest
Agency use of monitoring data
Coastal Plain Water Well Database