Record Display for the EPA National Library Catalog


Main Title Design Stream Flows Based on Harmonic Means.
Author Rossman, L. A. ;
CORP Author Environmental Protection Agency, Cincinnati, OH. Risk Reduction Engineering Lab.
Publisher c1990
Year Published 1990
Report Number EPA/600/J-90/470;
Stock Number PB91-182204
Additional Subjects Stream flow ; Water quality ; Water pollution standards ; Fourier analysis ; Mathematical models ; Concentration(Composition) ; Statistical analysis ; Risk assessment ; Water pollution effects ; Rivers ; Water flow ; Environmental protection ; Public health ; Study estimates ; Reprints ;
Library Call Number Additional Info Location Last
NTIS  PB91-182204 Some EPA libraries have a fiche copy filed under the call number shown. 07/26/2022
Collation 7p
Design streamflows are frequently used in water quality studies to provide adequate protection against pollutant exposure periods of a given duration. By analyzing the effect that simple streamflow dilution has on x-day average exposure levels of a pollutant, it appears that the x-day harmonic mean flow is a more meaningful statistic to use in computing design flows than is the customary arithmetic mean flow. The significance of the result was examined by computing design flows for sixty rivers throughout the country. For 7- and 30-day average annual low flows the impact was minimal. Substantial differences were found for the overall mean daily flow--a design flow suggested for use with water quality criteria based on protecting human health against lifetime exposures. The overall harmonic mean daily flow is typically 20 to 60 percent as large as the arithmetic mean daily flow. For ungaged streams it can be estimated from estimates of the arithmetic mean flow and the 7-day, 10-year low flow by regional regression analysis.