Iowa Geological Survey

Link to: Iowa Geological Survey Groundwater Information

NGWMN Contact:

Rick Langel

(319) 335-4102

richard-langel@uiowa.edu

The Iowa Geological Survey (IGS) is a water-level data provider to the National Groundwater Monitoring Network (NGWMN). IGS works to evaluate aquifer sustainability and provide historical records of water-level changes in state aquifers. In order to achieve these goals, IGS maintains a network of 60 monitoring wells, 40 of which are included in the NGWMN Portal. IGS has been a part of the Network since 2017.

IGS provides water-level data from the Cretaceous, Silurian-Devonian, Mississippian, and Cambrian-Ordovician aquifers.

Current NGWMN Projects:

2017: 7/1/2017 to 6/30/2019

Initial project to become a NGWMN data provider. IGS will provide water-level, well-construction, and lithology data to the Portal. The project is being done in conjunction with the Iowa Department of Natural Resources to provide water-quality data. The IGS will provide lithology and construction data for the Iowa Department of Natural Resources water-quality sites.

2018: 7/1/2018 to 6/30/2019

Project to do well maintenance at 7 of their NGWMN sites. They will initially purge the wells and then perform slug-tests on the wells. Their plan is to continue this work in the future so that the wells are reevaluated every 5 years.

2019 Round 1: 7/15/2019 to 12/31/2020

Project for well maintenance activities. Actives include periodic pumping of observation wells and initial hydraulic testing to establish a baseline connection at 13 wells.

2019 Round 2: 12/30/2019 to 12/29/2020

Project is to provide persistent data services for 1 year. The purpose is to ensure that NGWMN data is up to date and available. The IAGS will also begin work on upgrading services to WaterML2 and GWML2 standards.

2020: 7/15/2020 to 7/14/2021

Project is to do periodic pumping and well integrity testing on four wells.

2021: 7/15/2021 to 7/14/2022

Project is to do periodic pumping and slug testing of 5 wells

2022: 8/1/2022 to 7/31/2023

Project is to drill a replacement well in the Dakota aquifer and install water-level monitoring equipment in two Dakota wells to upgrade them to continuous water-level monitoring.

2023: 8/1/2023 to 7/31/2024

Project is to revise water-level web services, pump nine wells and modify an existing well, drill three new wells, and equip a well with continuous water-level monitoring equipment.

NGWMN Presentations:

Presentation at 2017 NGWMN New Data provider meeting

Site Selection and Classification

Site Selection 

The IGS selected wells from its' water-level network using t guidance provided inthe NGWMN Framework Document and the NGWMN Tip Sheets and in consultation with the USGS Staff.

Steps in the IGS selection process include:

1. Initial review and update, if necessary, of the metadata for the IGS network wells to ensure the metadata met the NGWMN minimum data requirements;
2. Identification of the geologic formation(s) that supply water to each IGS network well;,
3. Evaluation of the density of wells in specific aquifers.

The IGS selected 40 wells for inclusion into the NGWMN. The reasons for rejecting wells varies by aquifer. In the Mississippian aquifer, the IGS network consists of six (6) wells locatedin two (2) wellnests. Multiple wells are open to the same geologic formations at each wellnest. Only the well with the greatest penetration through the formation at each wellnest was selectedfor inclusion in the NGWMN. In the Silurian-Devonian aquifer, the IGS network contains twenty (20) wells located in six (6) wellnests and thirteen individual wells. Within the wellnests,multiple wells are open to the same geologic formations. Like the Mississippian aquifer, the well with the greatest penetration was incorporated into the NGWMN. Many of the IGS'Silurian-Devonian wells are in a single county, so some wells were rejected to maintain consistency with the NWMGN recommended well density. In the Lower Cretaceous aquifer,two (2) of the IGS' thirteen wells have been damaged to the point that reliable water-level measurements are not possible. The IGS is looking at its options, including well abandonment,for these wells. Since the future of these wells are unclear, the IGS decided not to add them to the NGWMN.

Site Classification 

The IGS assigned the 40 selected wells to subnetworks and monitoring categories using guidance obtained from the NGWMN& Framework Document and the NGWMN Tip Sheets.

Steps in the IGS selection process included:

1. Determining if each site had 5 years of data to start the Baseline Process,
2. Plotting and conducting linear regression analysis on water-level data to establish if trends exist in the data (trends established by the linear regression where tested at the 95% confidence level),
3. Establishing if the well was location with the 2, 5, or 10-year capture zone of a public well,
4. Identifying the number of "Water Use" wells that are within a 3 miles radius of the well. "Water Use" wells are wells that pump at least 25,000 gallons in a 24 hour period (examples of water use wells are public water systems, industrial wells, irrigations wells, and quarry dewatering wells) ,
5. Identifying the number of animal feeding operations within a 1 mile radius of the well, and
6. Evaluating groundwater model outputs to determine if the well is in an area subject to pumping pressure.

All the IGS network wells are dedicated monitoring wells and most have long-term water-level records. Consequently, all IGS network wells selected for the NGWMN are "Trend" sites. The classification of wells into subnetworks largely depended on the well location and the aquifer to which each well is open.

No major groundwater withdrawals occur near the NGWMN selected wells in the Cambrian-Ordovician and Mississippian aquifers. Consequently, the wells in these aquifers were assigned to the "Background" category.

The IGS Dakota aquifer groundwater model suggests many of the IGS wells in the Dakota aquifer are influenced by pumping stresses. Furthermore, declining water-level trends were identified in the linear regression analysis of many IGS Dakota wells. After consultations with IGS hydrogeologists, the majority of NWGMN selected wells in the Dakota aquifer were assigned to the "Suspected Changes" category.  The remaining Dakota wells, which are in areas not showing significant pumping influences or water-level declines, were assigned to the "Background" category.

The IGS network measure two distinct portions of the Silurian-Devonian aquifer. No major groundwater withdrawals occur in IGS wells in north-central Iowa. The wells in this area selected for the NGWMN were assigned to the "Background" category. However, the IGS wells in east-central Iowa are located near major cities and quarries. Thirteen of the wells selected for the NGWMN had multiple "water use" wells within a 3-mile radius and were assigned to the "Suspected Changes" category. Four wells, located farther away from cities, were assigned to the "Background" category. The water-levels in one well has been documented to decline with the pumping of nearby wells and was assigned to the "Documented" category.

Data Collection Techniques

The IGS uses the following established procedures to collect water-level measurements.

Version: 2018

PURPOSETo outline a standard procedure to ensure that accurate and consistent water-level measurements are made in the field.

MATERIALS AND INSTRUMENTS

• Steel surveyors tape, of appropriate length, graduated in 0.01 foot increments. Carpenters chalk.
• Electrical line or tape (sounder), graduated in 0.01 foot increments.
• Sonic sounder.
• Pencil or pen, blue or black ink.
• Water-level measurement field form, or handheld computer for data entry.
• Cleaner for tape (clorox diluted with water in a spray bottle, a container of disinfecting wipes, paper towel or cloth rag).
• Extra batteries.
• Tool kit (plumbers tape, wrenches, pliers, etc...).

ESTABLISH A SITE AND MEASURING POINTA clearly established measuring point (typically the top of the well casing), should be established where water levels are to be measured. Guidance for establishing a measuring point can befound in Cunningham and Schalk (2011). Document the distance between the land surface and the measuring point. The measuring point for a flowing well should be placed as close to the outlet as possible.

INSTRUCTIONSAll water level measurements should be conducted prior to any other activities occurring within the well.

Steel Tape Measurements

1. Apply chalk to the first several feet of the tape by pulling the tape across a piece of carpenters chalk resulting in a smooth coating of chalk on the tape.
2. Lower the tape into the well from the measuring point until a short length of the tape is submerged.
3. When the tape is submerged, hold the tape at the measuring point and read the value and record the "hold" value on the field form.
4. Retrieve the tape from the well and note the water mark, or "cut" mark, on the chalked part of the tape. Record the "cut" mark on the field form.
5. Subtract the "cut" reading from the "hold" reading to determine the distance to water below the measuring point. Record the resulting distance to water value on the field form.
6. Repeat the measurement by lowering the tape into the well a second time and "holding" at a point on the tape 1 foot greater than the initial "hold" point. Subtract the new "cut"mark and determine a second distance-to-water value for the well. If two measurements made within a few minutes do not agree within 0.02 foot repeat measurements until areason for the lack of agreement is determined, the results are shown to be reliable, or until it is determined that an accurate measurement is not possible.
7. After completing the water-level measurement, disinfect, rinse, and dry the portion of the tape that was submerged.

Electric Line (Tape) Measurements

1. Test the probe by dipping it in water and observing the indicator or by activating the "test" switch.
2. Lower the probe slowly into the well until contact with the water surface is indicated.
3. Read the electric line at the measuring point while the probe is just touching the water surface, and record the distance to water. Record the measurement on the field form.
4. Repeat the measurement. If the two measurements of static water level made within on minute do not agree within 0.02 foot, repeat the measurements until a reason for the lackof agreement is determined, the results are shown to be reliable, or until it is determined that an accurate measurement is not possible. Record measurement on field form.
5. After completing the water-level measurement, disinfect, rinse, and dry the portion of the tape that was submerged.

Sonic Measurements

1. Power on the probe and adjust temperature settings to the average air temperature in the well casing. Maps and tables found in the meter case provide data appropriate setting to use.
2. Use the cover cap (also found in the meter case) to cover the top of the well. Insert meter probe through small opening in cap.
3. Power on meter. Meter will emit five (5 "pings." Record the displayed measurement on field form.
4. Repeat the measurement. If the two measurements of static water level made within one minute do not agree within 1 foot, repeat the measurements until a reason for the lack ofagreement is determined, the results are shown to be reliable, or until it is determined that an accurate measurement is not possible. Record the measurement on the field form.

References

Cunningham, W.L., and Schalk, C.W., comps., 2011, Groundwater technical procedures of theU.S. Geological Survey: U.S. Geological Survey Techniques and Methods 1-A1, 151 p.

Data Management

Quality control is maintained by collecting two consecutive water level measurements within acceptable agreement for the procedure used. Field forms are scanned as PDFs and stored on the IGS file servers, which are backed up on schedules set by University of Iowa IIHR-Hydroscience & Engineering IT staff.

Data from the field forms are uploaded to the IGS' GeoSam database. IGS staff enter raw data into an Excel spreadsheet. Once all data has been entered into the spreadsheet, the staff member checks 10% of the records to verify the data are entered correctly. Any erroneous data found is corrected at this time.

Using a series of formula, the Excel spreadsheet generates an import file that contains all the required fields for GeoSam. The file is sent to IT staff to upload to GeoSam. After successfully loading the data to GeoSam, the IGS staff then checks 10% of the records against the field forms to ensure the data are correct. Any erroneous data found is corrected.

On a yearly basis, all data for a given well are graphed. Any point that is flagged as an outlier, for example results with values +/- 1.5 standard deviations from a trend line plotted through the data, is verified against the field forms to ensure the data are entered correctly.

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