SW Field Facilities & Offices

Delaware River Master

Hydrologic Instrumentation Facility (HIF)

HIF Intranet

HIF Labratory Facilities

Federal Interagency Sedimentation Project

USGS in Your State

USGS Water Science Centers are located in each state.

Other Water Sites

Office of Ground Water

Office of Water Quality

Office of Hydrologic Research

Cooperative Water Program

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Technical Resources for Frequency Studies

For questions and comments, contact email: h2osoft@usgs.gov.

Frequency analysis is used to fit annual time series of peak flows or low flows to a statistical distribution. The probability of events of specified magnitude being exceeded (peak flows) or not exceeded (low flows) can be calculated from the fitted distributions.

Programs and Scripts

PeakFQ: Flood Frequency Analysis. Based on Bulletin 17B. Includes Expected Moments Algorithm (EMA)

SWSTAT: Surface Water Statistics

WIE - Weighted Independent Estimates: ReadMe || FAQ || Version Info || Instructions || WIE Distribution Zip (all files included)

Useful References

Low Flow memos: Collection of Office of Surface Water Memorandum related to low flows.

Training Classes

SW1572 Frequency Analysis of Surface Water Statistics teaches frequency analysis techniques for both peak flows and low flows. The peak flow section includes an introduction to the Expected Moments Algorithm (EMA) for fitting frequency distributions. Class exercises using Microsoft Excel are designed to introduce students to concepts before PeakFQ and SWSTAT are used. (SW1572 Agenda--Word document)