Metadata: County Well Index (CWI) Version 4

County Well Index (CWI) Version 4

This page last updated: 07/18/2022
Metadata created using Minnesota Geographic Metadata Guidelines

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  1. Overview
  2. Data Quality
  3. Data Organization
  4. Coordinate System
  5. Attributes
  6. Distribution - Get Data
  7. Metadata Reference

Section 1: Overview

Originator:Minnesota Geological Survey

Title: County Well Index (CWI) Version 4

Abstract: The County Well Index (CWI) is a PC-based database system developed by the Minnesota Geological Survey for the storage, retrieval, and editing of water well information. Data is entered into the database by staff at the Minnesota Geological Survey and the Minnesota Department of Health. The database contains basic information on well records (e.g., location, depth, static water level) for wells drilled in Minnesota. The database also includes information on well construction, stratigraphy, and some water chemistry for many of the wells. The data are grouped together by county.

Most information in County Well Index is entered from the Water Well Driller Log form, which was submitted by the well driller to the Minnesota Department of Health at the time the well was constructed. Submission of a Water Well Driller Log is a requirement of the Minnesota Water Well Construction Code, passed by the State Legislature in 1974. While the County Well Index does not represent all wells in the state, it is the single most complete listing of state wells.

Purpose: CWI is used by a variety of local and state agencies, and by private groups interested in ground-water resource management.

Time Period of Content Date:

Currentness Reference: County Well Index is updated continuously. Approximately 10,000 new wells are drilled in Minnesota each year. Updated versions of the full CWI database are posted to the FTP site for distribution on a quarterly basis. See the readme file on the MGS FTP site for the exact date that the current distribution version of the database represents.

Progress: In work

Maintenance and Update Frequency: Quarterly

Spatial Extent of Data: Minnesota, statewide

Bounding Coordinates: -97.5

Place Keywords: Minnesota

Theme Keywords: inlandWaters, wells, water wells, ground water, stratigraphy, water levels, water chemistry, well construction, well management, county well index, CWI

Theme Keyword Thesaurus: ISO 19115 Topic Category

Access Constraints: None

Use Constraints: Acknowledgement of the Minnesota Geological Survey is appreciated in products derived from these data.

Contact Person Information: Jarrod Cicha, Subsurface Geologic Information Specialist
Minnesota Geological Survey
2609 Territorial Road
Saint Paul, MN  55114
Phone: 612-626-4108

Browse Graphic: None available

Associated Data Sets: 1. CWILOCS_NPS - a point GIS shapefile of all wells from CWI which have had their location field verified and digitized or GPS'd - is also available on the distribution CD and online from the ftp site. See:

2. UNLOCS_NPS - a point GIS shapefile of all wells from CWI which do not have a good location. Point locations for these wells are derived by calculating the midpoint of the Public Land Survey (Township-Range-Section-Subsections) locations reported by the driller. These calculated locations vary in accuracy; see location accuracy code. Downloads of this file, '' are available at the same location as the '' file:

3. To search or view well locations and associated County Well Index information, go to the Minnesota Department of Health website, Minneosta Well Index at

4. Data from many different agency data bases can be associated with the CWILOCS_NPS and UNLOCS_NPS shapefiles. Data is cross-referenced by Minnesota Unique Well Number (= RELATEID).

Section 2: Data Quality

Attribute Accuracy: No statistical attribute assessment has been performed. Some attributes of the well, such as PLS location, depth, casing diameter, and driller record, may be checked if the well is in an area where geological studies are being done (for instance, a County Geologic Atlas or Regional Hydrogeologic Assessment by MGS). For wells in these areas, locations are verified, and the driller's description of the geologic layers encountered is converted by MGS into interpreted lithologic codes and geologic formation codes. Otherwise, no verification is done of information on the well driller log. Older data which was originally entered into the MGS 'WELLOG' data base had been transcribed onto a coding form from the Water Well Driller Log, and keypunch data entry was done twice on each record in order to identify errors.

Note that the well owner name and address represents the owner of the well AT THE TIME THE WELL WAS CONSTRUCTED. Subsequent changes in ownership are not recorded in CWI.

Well records which have PLS locations reported to six quarter sections and which have Aquifer, Lithology, and Stratigraphy fields filled in are generally those which have been field-verified and interpreted by the Minnesota Geological Survey.

Logical Consistency: Not applicable

Completeness: Most of the records in CWI are for wells drilled since 1974, when the water-well construction code required that drillers submit records for wells drilled in Minnesota. These records are sent to the Minnesota Department of Health (MDH), who forward copies to the MGS. CWI does have records obtained through the cooperation of drillers and local government agencies for some wells drilled before 1974.

The County Well Index database DOES NOT represent all existing wells. Water Well Driller reporting has only been required since the State Water Well Construction Code was passed in 1974. Although older wells have been identified and added to the file in some areas, most pre-1974 wells are not represented. Since the law's enactment, driller compliance has been incomplete, although it is improving over time. Driller reporting of well location ranges from excellent to poor. Minnesota Department of Health well inspectors visit 10 to 25 percent of newly-drilled wells each year. GPS is used as a means of obtaining higher-accuracy locational data on inspected wells. The Minnesota Geological Survey and the Minnesota Department of Health have been committed to keeping the CWI up-to-date by adding all newly-drilled wells. Over time, the number of wells, the location accuracy and the geological cateogrization of the well information is improving.

For the most part, only water wells are represented on the database. Some exploratory boreholes along with monitoring well records are being added to CWI.

Horizontal Positional Accuracy:

Lineage: Since 1974 the state's Water-Well Construction Code has required that drillers submit records for wells drilled in Minnesota. These records are sent to the Minnesota Department of Health (MDH), who forward copies to the MGS. Since the early 1980's MGS has entered some information from water well driller logs into CWI. MGS also obtained well logs of pre-1974 from some drillers and entered this information into the system.

In 1997 the Minnesota Department of Health began entering all information from the well log into CWI for all new wells reported. When they were unable to keep up with all of the information, they entered complete well logs for all new wells drilled outside the 7-county metropolitan area, and summary information (the C4IX table information) for wells in the metro area. That left a backlog of additional well log information for new metro wells that was not in CWI.

As of 1999, MDH has been able to enter all information from the well logs for newly-drilled wells into the CWI database. Approximately 10,000 new wells are drilled in Minnesota every year.

The Minnesota Geological Survey edits and updates information already in CWI, and also is working to enter the backlog of well data not previously entered. MGS edits and updates consist largely of information that is gained during the course of geologic studies (such as County Geologic Atlases, Regional Hydrogeologic Assessments, and other work). For geologic studies, MGS verifies well locations, converts the driller information on layers encountered into geologic codes, identifies the aquifer, and makes other updates. Reported errors are corrected, and sometimes corrected or updated files received from other sources can be merged into the dataset.

Public Land Survey location information is stored in the CWI tables. Point file location used to create GIS files is stored on a separate file.

Section 3: Spatial Data Organization (not used in this metadata)

Section 4: Coordinate System

Horizontal Coordinate Scheme:

Horizontal Datum:

Horizontal Units:

Vertical Datum:

Vertical Units:

Depth Datum:

Depth Units:

Section 5: Attributes

Overview: Data for CWI are stored in 11 tables sharing the common field relateid. The relateid field is the primary key for the database, and is set in the index table C4IX. The 11 data tables are:

C4IX - main index table, summary information
C4ST - driller's description, interpreted stratigraphy
C4AD - address, both owner and contact
C4C1 - well construction information
C4C2 - additional construction information
C4ID - alternate identifier
C4PL - pump test information (simplified)
C4PT - pump test information ** not currently in use
C4PR - pump test results ** not currently in use
C4RM - remarks
C4WL - historic static water level information

Codes are stored in a separate database and are accessed by SQL requests. The code database contains lookup tables for code types. Code types are numerous, but cover all field entries where a specific text value is required. Examples would be fields such as stratigraphy, lithology, logical (i.e. Y/N/U), casing material, street identifier, or driller's license number. Code tables are internal to the Cwi4View version of the dataset.

Because of the size of the data set, maintaining a real time, updated set of well locations is not possible given the current hardware and software available at MGS. Because of this, well locations are stored in a separate database. This database can be linked to the CWI database by the field relateid, and contains UTM coordinates, projection information, coordinate source and coordinate method codes.

For more information:

Detailed Citation:

Table Detail:

Section 6: Distribution

Publisher: Minnesota Geological Survey

Publication Date: periodically revised

Contact Person Information: Jarrod Cicha, Subsurface Geologic Information Specialist
Minnesota Geological Survey
2609 Territorial Road
Saint Paul, MN  55114
Phone: 612-626-4108

Distributor's Data Set Identifier: cwi4

Distribution Liability: Data is provided "as is" without any warranty whatsoever, including but not limited to any warranty as to performance, merchantability or fitness for any particular purpose.

The entire risk as to the results of the use of this data is assumed by the user. MGS and MDH are not responsible for any interpretation or conclusions made by those who acquire or use it. MGS and MDH shall not be liable for any direct, indirect, special, incidental, compensatory or consequential damages or third-party claims resulting from the use of this data, even if they have been advised of the possibility of such potential loss or damage. In states that do not allow the exclusion or limitation of incidental or consequential damages, this data may not be used.

Ordering Instructions: To download from the MGS ftp site: - cwi data in Access2002 format - information on table formats and field definitions - associated gis data for located wells - associated gis data for unlocated wells

For further information and the specific date for the published dataset see the readme.txt file at the MGS ftp site.

NOTE: As requested by the Minnesota Department of Health, this version of CWI does NOT include records for public supply wells. For public supply well information, contact MDH staff:

Online Linkage: I AGREE to the notice in "Distribution Liability" above. Clicking to agree will either begin the download process, link to a service, or provide more instructions. See "Ordering Instructions" above for details.

Section 7: Metadata Reference

Metadata Date: 07/18/2022

Contact Person Information: Nancy Rader, GIS Data Specialist
Minnesota Geospatial Information Office (MnGeo)
658 Cedar Street, Room 300
St. Paul, MN  55155
Phone: 651-201-2489

Metadata Standard Name: Minnesota Geographic Metadata Guidelines

Metadata Standard Version: 1.2

This page last updated: 07/18/2022
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