In Reply Refer To:
Mail Stop 415

March 4, 2011


Subject: Technical resources for regionalization studies

Many Water Science Centers (WSCs) conduct studies to regionalize surface water statistics, typically using multiple linear regression. The purpose of this memorandum is to describe the Office of Surface Water (OSW) efforts to support regionalization projects being conducted by WSCs and to suggest actions that will help create more consistency amongst regionalization studies across the U. S. Geological Survey.

  1. The OSW has created a new website that contains information which should be useful for WSCs conducting regionalization studies; the website is at: This website will be updated with new software and guidance documents as they become available.
  2. Regionalization studies require an understanding of specialized statistical techniques. If appropriate technical expertise is not available within the WSC, the Water Science Field Team Surface Water Specialists (formerly Regional Surface Water Specialists) or OSW can assist a WSC in identifying available expertise in other WSCs. Due to the increasingly complex process, potential efficiencies of collaborative projects, and benefits of study areas that are based on hydrologic features rather than state boundaries, WSCs are encouraged to consider joint regionalization efforts involving two or more WSCs whenever possible.
  3. The regionalization study chief should attend the training course "Regionalization of Surface Water Statistics" (SW1523), prior to beginning work on the study or have equivalent experience. OSW plans to offer this class about once per year as long as there is sufficient demand.
  4. Water Mission Area policy requires that WSCs submit Cooperative Water Program study proposals through the Regional Executive Office for Water Science Field Team review. Water Science Field Team Surface Water Specialists have agreed to forward copies of regionalization proposals to OSW. A list of ongoing and proposed studies will be posted on the OSW regionalization website to facilitate identification of potential partner WSCs. If the regionalization study includes a StreamStats component, proposals should be sent to the StreamStats Development Team for review (as described in SW 2005.06) prior to submittal through the Regional Executive Office for Water Science Field Team approval.
  5. At the request of WSCs, OSW will assign an experienced statistical hydrologist from the OSW or a WSC to mentor the regionalization study chief and to provide technical guidance, as needed. The mentor can provide guidance in any phase of the project, including during proposal development. To be assigned a mentor, please contact Julie Kiang (, 703-648-5364) in the OSW.
  6. WSCs should develop formal workplans for regionalization studies. A suggested workplan is provided on the OSW regionalization website. The workplan should include a "launch meeting" near the beginning of the study to review objectives, statistical methodologies, and report preparation, and to identify needed technical resources and advisors to ensure success of the study. A "touchdown" meeting is also suggested to review study results and the study report. Specific timing of these meetings can be arranged according to the practices of the WSCs, but it is suggested that the launch meeting should be held no later than at the 15 percent completion point. Participants should include the study chief, Water Science Field Team Surface Water Specialist, and the OSW designated project mentor, if applicable.
  7. Regionalization reports must thoroughly document the development of data and the regionalization process. The OSW has drafted a suggested regionalization report outline, posted on the OSW regionalization website. The report should contain sufficient information that a future analyst could reproduce the study. To further facilitate future analysis, important project files should be archived. Such material includes input files and output files for the final regression equations, data used for the calculation of basin attributes, and data and procedures used to estimate flow statistics (including input and output files, if software such as PeakFQ or SWSTAT were used).

Stephen F. Blanchard /signed/
Chief, Office of Surface Water

U.S. Geological Survey
National Center, MS 415
12201 Sunrise Valley Drive
Reston, VA 20192


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