A wide variety of approaches have been adopted to quantify runoff variability, with differing degrees of emphasis on high flows (floods), low flows, seasonal variation of flows, and annual flows, and many of these are discussed in other chapters of this book. An additional feature of runoff variability that has considerable practical relevance is the period of time runoff remains higher than a specified magnitude, otherwise known as “flow duration”. The flow duration curve (FDC), which is the subject of this chapter, is a graphical representation of the frequency, or the fraction of time (hence the word, duration) during which a specified magnitude of runoff is equalled or exceeded. Representation of the entire runoff hydrograph time series (typically daily runoff, but it can also be hourly, or even monthly) in the form of the FDC makes the latter a compact signature of runoff variability, and a valuable tool to diagnose rainfall-runoff responses in gauged catchments at a holistic level, and to regionalize them to ungauged catchments. However, by representing runoff variability in the frequency domain as the FDC, information on the timing of the runoff response is lost. This is reflected in the basin’s runoff seasonal flow regime (Chapter 6), and of course, in the complete runoff hydrograph (see Chapter 10). FDCs (for daily runoff) can be constructed empirically for gauged sites by (1) ranking observed runoff in ascending order and (2) plotting each ordered observation versus its corresponding duration (e.g. in days), or its fractional duration (which is dimensionless). Comparisons of FDCs between catchments of different sizes or in different climatic regions can be assisted by expressing the FDC in terms of normalized runoff (normalized by drainage area or by mean annual runoff). If a stronger emphasis is needed to be given to either the low flow or flood portion of the FDC, then it can be plotted semi-logarithmically, expressing the logarithm of runoff as a function of (fractional) duration.
Attilio Castellarin, G. Botter, D.A. Hughes, S. Liu, T.B.M.J. Ouarda, J. Parajka, et al. (2013). Prediction of flow duration curves in ungauged basins. Cambridge : CAMBRIDGE UNIVERSITY PRESS.
Prediction of flow duration curves in ungauged basins
CASTELLARIN, ATTILIO;
2013
Abstract
A wide variety of approaches have been adopted to quantify runoff variability, with differing degrees of emphasis on high flows (floods), low flows, seasonal variation of flows, and annual flows, and many of these are discussed in other chapters of this book. An additional feature of runoff variability that has considerable practical relevance is the period of time runoff remains higher than a specified magnitude, otherwise known as “flow duration”. The flow duration curve (FDC), which is the subject of this chapter, is a graphical representation of the frequency, or the fraction of time (hence the word, duration) during which a specified magnitude of runoff is equalled or exceeded. Representation of the entire runoff hydrograph time series (typically daily runoff, but it can also be hourly, or even monthly) in the form of the FDC makes the latter a compact signature of runoff variability, and a valuable tool to diagnose rainfall-runoff responses in gauged catchments at a holistic level, and to regionalize them to ungauged catchments. However, by representing runoff variability in the frequency domain as the FDC, information on the timing of the runoff response is lost. This is reflected in the basin’s runoff seasonal flow regime (Chapter 6), and of course, in the complete runoff hydrograph (see Chapter 10). FDCs (for daily runoff) can be constructed empirically for gauged sites by (1) ranking observed runoff in ascending order and (2) plotting each ordered observation versus its corresponding duration (e.g. in days), or its fractional duration (which is dimensionless). Comparisons of FDCs between catchments of different sizes or in different climatic regions can be assisted by expressing the FDC in terms of normalized runoff (normalized by drainage area or by mean annual runoff). If a stronger emphasis is needed to be given to either the low flow or flood portion of the FDC, then it can be plotted semi-logarithmically, expressing the logarithm of runoff as a function of (fractional) duration.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
