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SYNTHESIS OF FLOW‐DURATION CURVES FOR UNREGULATED STREAMS IN NEW HAMPSHIRE 1
Author(s) -
Dingman S. Lawrence
Publication year - 1978
Publication title -
jawra journal of the american water resources association
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.957
H-Index - 105
eISSN - 1752-1688
pISSN - 1093-474X
DOI - 10.1111/j.1752-1688.1978.tb02298.x
Subject(s) - evapotranspiration , snowmelt , elevation (ballistics) , structural basin , streams , hydrology (agriculture) , environmental science , flow (mathematics) , streamflow , precipitation , drainage basin , stream flow , geology , snow , mathematics , meteorology , geography , geomorphology , geotechnical engineering , geometry , cartography , ecology , computer network , computer science , biology
Flow‐duration curves are concise pictures of flow variability at a point on a stream, and provide essential information for all water‐resource planning. In New Hampshire, useful estimates of flow‐duration curves for ungaged points on unregulated streams can be made using only information readily available from contour maps: 1) area of the basin above the point of interest; and 2) either the measured mean basin elevation or the elevations of the highest and lowest points in the basin. Measured or estimated mean basin elevation is then used in regression equations to estimate mean flow QC and the flow exceeded 95% of the time, Q 95 . QC is assumed to occur at the 27% exceedance frequency. Q 02 , Q 05 , and Q 30 are estimated as multiples of QC. Equations are provided for calculating 95% confidence intervals for future estimates using the method. The dependence of mean flow on elevation is due to positive vertical precipitation gradients and negative vertical evapotranspiration gradients. The dependence of Q 95 on elevation appears to be due largely to the fact that it rains more often, that snowmelt takes longer, and that evapotranspiration is reduced at higher elevations.