Iowa Department of Natural Resources

Link to:  Iowa Department of Natural Resources Groundwater Information

 

NGWMN Contact:

Claire Hruby

(515) 725-8348

claire.hruby@dnr.iowa.gov

 

The Iowa Department of Natural Resources (IADNR) is a water-quality data provider to the National Groundwater Monitoring Network (NGWMN). IADNR samples raw water annually from 137 public water supply wells with data collected in some wells as early as the 1960s. The goals of the network are to 1) characterize groundwater quality by aquifer and regions, 2) evaluate long-term trends, and 3) to address new or emerging issues. IADNR serves data from 115 sites to the NGWMN Portal. IADNR has been a part of the Network since 2017.

IADNR provides water-quality data from the Glacial sand and gravels, Cambrian-Ordovician, Lower Cretaceous, Silurian-Devonian, and the Mississippian aquifers.

 

NGWMN Projects:

2017: 7/1/2017 to 6/30/2018

Initial project to become a NGWMN data provider.  Data is available from a network of 115 public water supply wells where raw water is sampled. The project was done in conjunction with the Iowa Geological Survey. The Iowa GS  provides well-construction and lithology data to the portal for Iowa DNR water-quality sites.

2019: 11/15/2019 11/14/2021

Project is to support persistent data services for 2 years. The purpose is to ensure that NGWMN data is up to date and available.

NGWMN Presentations:

2017 presentation at NGWMN new data providers meeting

 

Site Selection and Classification

Site Selection

115 wells were selected for the NGWMN from the 137 candidate wells in the IADRN ambient water-quality network. The criteria used to select these wells were as follows:

  1. Wells must have adequate lithological and construction data to make aquifer assignments and to estimate capture zones.
  2. Wells must have been sampled multiple times since 2014. This criteria ensures that the well is still being actively maintained by the municipal water supply and that the current water operator is cooperative. The majority of the wells selected are active wells; however, a few wells are considered "standby" wells maintained for purposes other than drinking-water, such as fighting fires.
  3. Wells must have been monitored as part of the network for a minimum of 3 years. Monitoring results are sufficient to assign subnetworks and monitoring categories or are expected to meet the 5-year criteria for assignment of categories in the near future. Some of the wells selected have been sampled as many as 11 times since 2002, and a few have been sampled as far back as the 1960's by the USGS and the Iowa Geological Survey (called the Geological Survey Bureau at the time).
  4. No more than one well per aquifer per community.
  5. Wide spatial distribution within the aquifer, with some preference for areas of higher aquifer use. Wells are sparse in the south-central region of the state, where most communities rely on surficial water supplies. Numbers of available wells were below the maximum recommended number of water quality sites for all aquifers, with the exception of sand and gravel aquifers - glaciated regions (N100GLCIAL). In Iowa, the groundwater quality of Pleistocene Series (112PLSC) and Holocene Alluvium (111ALVM) local aquifers are very distinct in terms of water quality and vulnerability to contamination from surface activities. In general, alluvial aquifers are highly vulnerable to surface contamination, whereas Pleistocene buried sand and gravel aquifers are confined and more likely to contain "natural" rock-derived contaminants. Most Pleistocene Series wells are confined and occur within the Des Moines Lobe landform region in north-central Iowa, while wells in Holocene Alluvium are all unconfined and more widely distributed around the state. We observed that in other neighboring states, the alluvial aquifers were classified separately and there was no maximum number of sites recommended.

Site Classification

Water-quality results were used to assign subnetworks as follows:

Documented Changes (52 wells)

Suspected Changes (1 well) had at least two of the following:

Background Conditions (35 wells)

Unclassified (27 wells)

IDNR has observed that the majority of anthropogenic water quality changes occur in wells with less than 100 feet (30 meters) of confining materials, and the most vulnerable wells have less than 50 feet of confining materials above the water-bearing unit.

IADNR identified 58 trends wells and 57 surveillance wells within their network. Details on this categorization can be found in the Final Report.

 

Data Collection Techniques

For basic chemical constituents, Iowa DNR and our partner water supply operators refer to collection techniques outlined in the USGS National Field Manual for the Collection of Water-Quality Data.

Modifications of USGS protocol are necessary in some instances. Thus, the following steps are also required:

  1. In-lieu of measured purge volumes, all wells are required to be pumped a minimum of 30 minutes.
  2. Phone contact is established with all water operators each year to ensure willingness to sample, correct shipping locations, explain any variations to sampling protocols, and update the status of wells.
  3. Well tag ID's are installed on most water supply wells and all forms include reference to both the local well number and the Tag ID number.
  4. All laboratory instructions for specific bottles, fill instructions, holding, transport, and shipping are followed.
  5. Pre-printed labels are used whenever possible to avoid mislabeling.
  6. Only certified water operators and trained agency staff are permitted to sample.
  7. Complete all chain-of-custody paperwork.

A list of analytes and accredited laboratories used by IADNR can be found in the Final Report.

 

Data Management

The IADNR quality assurance processes include: 

  1. Field:
    1. Duplicate samples are collected at 10% of sites, and 2-3 blanks are collected per sampling season. Published SOP's for data collection are followed at all times, including use of protective gear, "clean-hands/dirty-hands" protocols, and limited exposure to pharmaceuticals or personal care products when appropriate
  2. Laboratory
    1. Laboratory QA/QC protocols, including standards and controls, spiked samples, lab blanks, and laboratory duplicate analyses are documented by individual laboratories
  3. Database
    1. Analytical results submitted to the EQuIS database are checked against laboratory reports to ensure accurate data migration has occurred. Look-up tables are used when possible to promote standardized data entry.
  4. Reporting
    1. Publications are reviewed internally by a review team prior to publication. Reports formulated in cooperation with IGS, USGS, EPA, and other collaborators follow review processes as required by these organizations.

All Minimum Data requirements required to be submitted via the Well Registry, including location information, accuracy, aquifer codes, site type, confinement status, and well depth were uploaded. National aquifer codes used during the initial upload are based on previous USGS classification efforts. IDNR believes some (<10) of these sites have been miscoded and is working with IGS and USGS staff to agree on final classifications. Any changes will be corrected in the well registry.

Lithologic (L) and well construction (C) data are provided via the Iowa Geological Survey's GeoSam database. Linkage to GeoSam was established using web services provided under a separate grant. All sites chosen for the network have well logs available and many have chip samples stored at the Geological Survey's Oakdale facility. However, detailed lithologic descriptions have not been created for all sites. Continued joint efforts between the IDNR and the IGS is ongoing to complete lithologic descriptions. Well screen and well casing details are also not available for all sites. Given that the USGS has used these wells for monitoring for several decades, we are confident that they are currently the best representation of Iowa's ambient groundwater quality that is available to us at this time. If other agencies or resources become available to improve our knowledge of these details or to install dedicated monitoring wells, we will certainly be willing to modify our well selection in the future.

Water quality data are linked via the WQX portal, thus no web service development was necessary.

 

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