In Reply Refer To: January 7, 2009
Mail Stop 411


Subject: Update on Guidance for the Preparation, Approval, and Archiving of Aquifer-Test Results

Analyses of aquifer tests to define the hydraulic characteristics of a specific aquifer or aquifer system are an integral part of our interpretive ground-water investigations. The results of these analyses are critical components of flow-system or solute-transport analyses and important to conclusions published in U.S. Geological Survey (USGS) reports. Consequently, reported aquifer characteristics such as hydraulic conductivity, transmissivity, storativity and other hydraulic characteristics derived from aquifer-test analyses must be clearly documented and technically defensible. The purpose of this memorandum is to reiterate guidelines and procedures necessary to obtain approval for the results of aquifer tests and to provide guidelines for archival of the test results. This memorandum is an update of Office of Ground Water Technical Memorandum 94.02.


According to WRD Publications Guide (U.S. Geological Survey Open-File Report 87-0205, Article 11.01.2) "....calculated hydraulic characteristics such as transmissivity, hydraulic conductivity, and storage coefficient, are interpretive and must be approved by the Director, unless cited from a Director-approved report." Approval of aquifer tests is currently delegated to the Regional Ground-Water Specialists. Approval is required for all calculations of aquifer hydraulic characteristics to be released to the general public, to cooperators, or published in or otherwise used to support the results of investigations reported in USGS-approved reports.

Estimates of aquifer hydraulic characteristics commonly are obtained from "textbook" or published values for various lithologies. These are not considered calculations of aquifer characteristics and do not require approval under the terms of this memorandum. In addition, estimates of transmissivity determined on the basis of specific-capacity measurements do not require approval. Results from well-performance tests (typically slug tests) that are used to check the connection of observation wells with the aquifer also do not require approval, unless they are used to report on aquifer characteristics.


While the USGS encourages the publication of aquifer-test results in reports, it is not feasible to publish the data and graphical results for every test conducted. In all cases, either as part of a formal report or as a separate packet (for archival), aquifer-test results should be submitted to the Regional Ground-Water Specialist for review and subsequent approval. The Regional Ground-Water Specialist reviews the report or aquifer-test packet to assess (1) that the report or packet contains the necessary data and related information to properly analyze the subject test(s), and (2) that the analyses and results are technically defensible.

Elements that typically should be submitted for review are listed below. These elements assume an aquifer test that is comprised of a pumping well and one or more observation wells and should be modified as appropriate for other types of tests such as a single-well slug test. The eight elements are as follows:

  1. A brief description of the test which includes the purpose, date, test procedures, and methods of analysis of the results. Any unique or unusual features or problems related to the test or to the collection and analysis of test data should be described. A brief description of the assumptions used in analyzing the test results also should be included, as needed to clarify the test.

  2. A sketch of the test site showing the distances from the pumped well to all observation wells and the location of any boundaries, streams, springs, ditches, pumping or flowing wells, or other features that possibly could influence test results. Where the test includes multiple wells, the sketch of the test site should be drawn to scale.

  3. Description of test and observation well construction, including screened and open interval(s), casing and screen diameters, and location of filter pack and grouted intervals.

  4. A description of the site hydrogeologic characteristics, including sections that show the major water-bearing and confining units. The intervals of the pumping and observation wells that are screened or open should be depicted on the logs or sections.

  5. Complete time-discharge records of the pumped well.

  6. Complete water-level records and hydrographs showing pre-test trends and water levels during the pumping and recovery phases.

  7. Description of methods and computations showing adjustments to drawdown for pre-test trends, adjustments of recovery for projected drawdown, or adjustments to account for extraneous effects not related to pumping or recovery, such as barometric and tidal effects or other interferences.

  8. All plots of observed or adjusted drawdown or recovery data used to determine hydraulic characteristics, showing match points (when used) and computations.

It is recognized that in some cases it is not possible to provide a complete description of these eight elements. Investigators are encouraged to discuss their plans with the Regional Ground-Water Specialist to determine the requirements for a particular test packet or report before submitting it for review and approval.

A transmittal memorandum, indicating that the test results have been reviewed by the Science Center Ground-Water Specialist or their designee, shall be included with the aquifer-test packet or report. This review should include some checking of the field data and a verification that the test results are appropriate, given the site hydrogeology, well construction, and test conditions and that the test results have been reviewed independently before being submitted for regional review and approval.

Following approval by the Regional Ground-Water Specialist, the packet or report will be returned to the originating Science Center or office where the hydraulic characteristics and related site and well data should be entered into the National Water Information System (NWIS) and the packet and associated information appropriately archived in a Science Center "aquifer-test archive." These archived aquifer-test files should include the approved aquifer-test packet and the packet-review transmittal memoranda. The aquifer-test archive will be reviewed as a routine part of Science Center ground-water technical reviews.

If computer software is used in the aquifer-test analysis, the policy outlined in Office of Ground Water (OGW) Technical Memorandum 91.04 and clarified in OGW Technical Memorandum 97.01 must be followed. This policy requires that the theoretical basis of the software be documented and that it be demonstrated that a test-data set can be correctly analyzed using the software. Submittal of a computer-software analysis does not eliminate the need for the information described in element 8, above.

The aquifer-test archive can be a paper or electronic archive (or usually a combination of both). Most current aquifer tests will have electronic data collected as a part of conducting the aquifer test (for example, output from a pressure transducer or data logger). These electronic data must be archived. The Science Center has the option of archiving these data in the ADAPS (Automated Data Processing System) subsystem of NWIS or in a local on-line electronic archive subject to the Science Center’s regular computer backups. If both a paper and an electronic archive exist, there should be a cross reference indicating the existence of each. That is, the electronic archive should include a “read-me” file explaining where the paper archive is physically located, and the paper archive should include a notation describing the location of the electronic archive.

In the electronic aquifer-test archive, a sub-directory should be created for each aquifer test (or project) and named according to the associated project report (for example, SIR2007-2083 Cedar Rapids) or site location (if the results are not included in a project report). All output from the data-collection equipment should be included in this archive system (for example, data logger output files, output files from data-analysis programs such as AQTESOLV, and summary data files created in other software packages such as Excel). If possible, all files should be saved as text files (ASCII), in addition to any proprietary formats, to ensure that they remain available even if proprietary software changes.

This memorandum discusses documentation, approval, and archival procedures in the context of single- or multiple-well aquifer tests. Aquifer characteristics also may be calculated by other methods, such as, determination of aquifer diffusivity from attenuation of a tidal pulse or flood wave through an aquifer, or using hydrograph-recession characteristics. The same procedures should be followed for these types of analyses, and information in the report or packet must adequately enable reviewers to visualize the physical system, evaluate all data, verify all calculations, and assess that the methods and results are defensible.

In summary, reported aquifer characteristics that are calculated from aquifer tests must be clearly documented and technically defensible. As such, it is required that: (1) the author prepares a formal report or aquifer-test packet that includes the eight elements outlined in this memo; (2) the report/packet is submitted to the Science Center Ground-Water Specialist (or their designee) for technical review of aquifer test analyses; (3) the Science Center Ground-Water Specialist (or their designee) prepares a formal memo of review; (4) the author addresses the Science Center Specialist’s comments and transmits the report/packet to the Regional Ground-Water Specialist for aquifer-test review and approval; and (5) once approved, aquifer test results must be archived and entered into NWIS.

William M. Alley /signed/
Chief, Office of Ground Water

This memorandum supersedes Office of Ground Water Technical
Memorandum No. 94.02