Montana Water Resources Data Reliability

Information about Data Reliability

Considerable effort has been made to ensure the accuracy of the information in our data-base. However, errors may exist. If you have any concerns about the accuracy of the data you retrieve from these pages,  please contact us. 

This page presents a brief introduction to the reliability of the various types of water-resources data served by the USGS. Specific sections are provided for real-time, surface-water, ground-water, and water-quality data, and site-location  information.

Additional information is available from the national USGS Program Offices:

Ground Water

Surface Water

Water Quality

Reliability of Real-Time Data

Data from real-time gages are relayed to the Montana District office in Helena through the Geostationary Operational Environmental Satellite (GOES) data-collection system. Data are transmitted from each station at intervals of either 3 or 4 hours and are loaded into the Montana District computer system.

Real-time data are PROVISIONAL data that have not been reviewed or edited. These data may be subject to significant change and are not citeable until reviewed and approved by the USGS. Real-time streamflow data may be changed after review because the stage-discharge relationship may have been affected by:

• Backwater from ice or debris such as log jams
• Algal and aquatic growth in the stream
• Sediment movement
• Malfunction of recording equipment

Data users are cautioned to consider carefully the provisional nature of the information before using it for decisions that concern personal or public safety or the conduct of business that involves substantial monetary or operational consequences.

Reliability of Surface-Water Data

Data are reviewed periodically to ensure accuracy. Each station record is considered PROVISIONAL until the data are published. The data are usually published within 6 months of the end of the water year.  Information concerning the accuracy and appropriate uses of these data or concerning other hydrologic data may be obtained by contacting the individual listed on the data page.

Reliability of Ground-Water Data

All information in the ground-water database is provisional and subject to revision. The data have been collected and entered for a wide variety of projects and purposes over a long period of time and the resulting database varies in quality and detail. The information includes data measured by USGS personnel and data reported by others.  Many other Federal, State, and local agencies use the same well-numbering system that is used in this database; consistency of assigned well numbers between agency databases should not be assumed. The USGS database does not include all wells in Montana.

Reliability of Water-Quality Data

Water-quality data for Montana are available for retrieval through the end of the 1999 water year (through September 30, 1999). These data have been approved by the USGS and published. Provisional water-quality data generally are not available for the current year because of the many quality-assurance checks needed to verify either the acceptability of, or the need to revise, laboratory results.

Information about water-quality data is available at the following Web page:

• Nwisweb Water Quality help page

Users are cautioned that the quality of water-quality data may differ over time as a result of changes in sampling and analytical methods, improvements in equipment and sample-processing procedures, and increased implementation of quality-assurance practices. If users intend to make comparisons between recent and older data, it is important to note that improvements in precision and accuracy over time may render older data less reliable and, in some instances, unsuitable for evaluation of trends. This is especially true for trace elements for which new protocols have been developed and implemented nationally by the USGS since the early 1990's.

Interpretations based on retrieved data are the responsibility of the user. The USGS cannot provide interpretation upon request because of the requirement that all interpretive assessments conducted by the agency be technically reviewed, approved, and made available to the public through a formal process. Although resources are not available to provide that level of assistance, information concerning the accuracy or appropriate uses of the data for particular sites or areas within Montana may be obtained by contacting the office listed on the data page.

Reliability of Site-Location Information

Information about the site location has been entered into the various computer databases over the decades using the latest maps and location information available at the time. Although locations are updated as needed, some older, discontinued sites may not have had the site information checked or updated recently. Information such as latitude and longitude and other data may not be accurate with regard to today's standards or information. For surface-water sites, the site name is based on the name of the stream, or lake if appropriate, and location information such as highways, bridges, and the nearest Post Office or town. Many older sites are referenced to towns that are many miles from the site, or towns that may have been incorporated into newer or larger towns or cities. If you have any questions about the information about any site(s), please use the links to ask.