Minnesota Department of Natural Resources
Link to: Minnesota Department of Natural Resources Groundwater Information
NGWMN Contact:
Matthew Meyer
651-539-2110
matthew.meyer@state.mn.us
The Minnesota Department of Natural Resources (DNR) is a water-level data provider to the National Groundwater Monitoring Network (NGWMN). DNR has over 1,000 actively monitored well sites, many of which are measured quarterly, and has extensive historical groundwater records. Currently, DNR serves 375 sites to the NGWMN Portal. DNR has been a part of the Network since 2017.
DNR provides water-level data from the Cambrian-Ordovician, lower cretaceous and upper carbonate aquifers.
NGWMN Products:
NGWMN Projects:
Initial project to become a NGWMN data provider. The DNR participated as a pilot project for the NGWMN, but subsequent updates to their databases require development of new web services. Also the pilot project focused on a single principal aquifer. This project completes the well selection and classification process for the rest of the water-level sites in Minnesota.
Project provides persistent data services, does well maintenance, and supports well drilling. Well maintenance activities at 25 wells will include specific-capacity testing, video logging, and well redevelopment (where needed). They will be drilling 5 new wells to fill gaps in the NGWMN.
Project will drill 25 new wells to fill gaps in the NGWMN. Four of the wells will be deep bedrock wells in theCambrian-Ordovician aquifer and the other 21 wells will be shallow wells in unconsolidated sediments throughout Minnesota.
Project is to drill 5 new wells at a nested site.
2022: 7/15/2022 to 6/30/2024
Project is to upgrade equipment at 26 wells from stand-alone loggers to telemetered observation wells.
NGWMN Presentations:
2017 Presentation at NGWMN new data providers meeting
Site Selection and Classification
Site Selection
**In 2017, as a new data provider to the USGS National Groundwater Monitoring Network, DNR reviewed possible sites for network inclusion based on:
- Site is a dedicated Observation Well, or for the sole purpose of monitoring groundwater levels,
- Site is monitored regularly by Soil and Water Conservation District staff or DNR staff,
- Geographical position within national and local aquifers,
- Meets spatial density requirements within national aquifers of interest,
- Site read status, with preference for actively monitored sites,
- Types of data provided with preference for sites that have both continuous and discrete data, and
- Status of wells connection to the aquifer with preference on wells with good connection or recent maintenance; good slug test results.
Priority was placed on wells that have a period of record at least a minimum of 5 years.
Site Classification
In 2017, the sites selected to provide data to the USGS NGWMN were predominantly:
Subnetwork: Background
Monitoring Category: Surveillance and Trend
Since observation wells are dedicated groundwater level monitoring sites -monitoring either baseline or background groundwater levels, a majority of sites provided to the USGS NGWMN fall into "Background" subnetwork by default. Observation wells are generally not used as water supply sources, are situated in areas to avoid significant drawdown events and not situated near large surface bodies of water.
Observation wells, however, may meet the criteria of "Suspected Changes" and "Documented Changes," especially those of long-term monitoring. Revisions to the well registry subnetwork classification are ongoing as analysis is performed. Observation wells of "Documented Changes" are considered rare given the nature/purpose of observation wells.
Through review, observation wells were classed as either "Surveillance" or "Trend" monitoring categories. There are no "Special Studies Monitoring" wells included with the groundwater sites provided to USGS NGWMN. Observation wells are monitored frequently by at least, 8 measurements annually, and in the subset of wells provided to the USGS NGWMN, supplemented with continuous data. Wells that were classified as "Surveillance" monitoring wells are generally situated closely to metropolitan centers.
Sites fulfill trend monitoring and surveillance monitoring needs. A majority of sites that can be classified as trend monitor sites will have periods of record at least a decade in length. Surveillance monitor sites are more common in high population areas and closer together in proximity. DNR research has been conducted with many groundwater sites and will be able to identify wells that meet the criteria for various subnetworks that of background conditions, suspected changes and documented changes.
For "Trend" sites, DNR will use database queries of PostgreSQL to focus on a site density of 1 to 8 sites per 1000 square miles in each Principal or Major aquifer. DNR has Nested wells has 214 active nested wells for consideration as "Trend" sites. Area and groundwater monitoring hydrologists will use NGWMN tip sheet criteria to classify sites appropriately for consideration for data sharing with NGWMN.
Surveillance sites can be referenced to a nearby trend site and with DNR's extensive groundwater monitoring network, a density of 3 to 7 surveillance sites per trend site is possible to reflect local conditions within the aquifer. Area and groundwater monitoring hydrologists will use NGWMN tip sheet criteria to classify sites appropriately for consideration for data sharing with NGWMN. Hydrologist supervisors and division director may assist in identifying sites for data sharing with NGWMN.
In a relatively undeveloped aquifer water levels may vary less spatially, therefore fewer surveillance wells may be required. In a more developed aquifer water levels may be more spatially variable, so more surveillance sites may be required.
Data Collection Techniques
DNR collects their data according to the following methods:
- Determine where "Measuring Point" (MP) is located on the well, generally indicated by a demarcation. Typically, this will be the top of the free-standing casing. However, there may be circumstances where the MP will be an access plug located elsewhere. Irrigation, or other high capacity, wells often have a plug near the base of the turbine or have an access tube angling off from the turbine base. If in question about the location of the MP, do one of two things: check the height of the MP described on the data sheet, it may lead to the proper location or, call the Groundwater Level Database Manager in St. Paul for clarification.
- Attaching a weight to the end of the steel tape is optional and should never be done in situations where the well contains any obstructions, including submersible pumps, pitless adapters or turbines.
- Chalk enough tape to exceed the expected DTW with 5 feet typically sufficient. Tapes often get wet above the water level, e.g. due to condensation in the well casing. If this is not noticed and dried off, the next reading could be impaired, and additionally, make it more difficult to re-chalk as a wet tape will not hold the chalk effectively.
- Cold weather is usually the most difficult time to use a steel tape because color change is less evident when the water on the tape freezes and the freezing water is hard to remove from the tape. When possible, take two tapes along when it is below freezing and leave one on the dash to dry while the other is used. Wipe the steel tape dry and then coat the end with carpenter's chalk. To do this, unreel a portion of tape (5 ft is usually sufficient) and, while holding the reel in one hand, press the chalk against the numbered side of the tape and pull it along toward the free end until the unreeled tape is coated with the light blue chalk.
- Lower the chalked tape into the well until some of the chalked portion is in water. Continue lowering slowly until a whole-foot mark on the tape is exactly at the measuring point. Record this measurement on the data sheet as "Tape Held". Do not allow the tape to fall past this chosen "hold"; to do so would result in an erroneous reading.
- Reel up the tape and carefully read the measurement (to the closest hundredth of a foot, 0.00') at the point where the chalk becomes wet and turns to a dark blue color. This is the "Wetted Length" measurement and should be recorded on the data sheet.
- Subtract the Wetted Length from the Tape Held and record the result on the data sheet as "Depth Below Measuring Point"
- Use the "Comments" column to report anything that may have affected the water level such as a nearby pumping well, irrigation, drainage of nearby water body, standing water, damage to well, etc. If the well has been damaged, contact the Obwell program as soon as possible. Data accuracy to the 0.01 foot is possible with this method of measurement.
Data Management
Groundwater data is actively reviewed for completeness, accuracy and detail, if necessary. The groundwater level coordinator plays a forefront role in data review activities as well as DNR staff who play significant roles in quality checks and peer-review.
Once groundwater level measurements have been reviewed for data quality, data is stored in the PostgreSQL database as an approved observation and data is copied over to the Hydstra database, and output onto the CGM within 24 hours. Time Series Data is similarly quality checked, albeit in a different manner.
- Logger/pressure transducer installed are programmed to take hourly water level readings,
- Hand measurements are taken with either a steel tape, or an electronic tape from a known measuring point to calibrate the logger in the field, if needed,
- Logger data is downloaded quarterly and hand measurements, typically using Electric Tapes, are performed at time of logger download to ensure logger data accuracy and inspect for electronic drift,
- Data from loggers come in the form of CSV files and are uploaded to Observation Well Database web input and then imported to Hydstra on an hourly basis,
- Groundwater level coordinator will review the logger data and ensure all measurements entered Hydstra and values are correctly recorded in CSV with depth to water, both non and barometrically-corrected correctly categorized, water temperature in Celsius and air temperature, if any,
- Corrupted files are further investigated for errors and partners notified, and
- All data corrections are handled in Hydstra.