Hydrograph separation: an impartial parametrization for an imperfect method (original) (raw)

This paper presents a new method for hydrograph separation. It is well-known that all hydrological methods aiming at separating streamflow into baseflow and quickflow present large imperfections, and we do not claim to provide here a perfect solution. However, the method described here is at least (i) impartial in the determination of its two parameters (a quadratic reservoir capacity and a response time), (ii) coherent in time (as assessed by a split-sample test) and (iii) geologically coherent (an exhaustive validation on 1,664 French catchments shows a good match with what we know of France's hydrogeology). Last, an R package is provided to ensure reproducibility of the results presented. 1 Introduction Hydrograph separation and the identification of the baseflow contribution to streamflow is definitely not a new subject in hydrology. This age-old topic (Boussinesq (1904); Horton (1933); Maillet (1905)) is almost as universally decried as it is universally used. Indeed, two adjectives appear repeatedly in hydrology textbooks: artificial and arbitrary (see. e.g., Linsley et al. (1975); Réméniéras (1965); Roche (1963); Chow (1964)). Hewlett and Hibbert (1967)-the famous forest hydrology precursorseven added desperate, where Klemes (1986) compared the hydrograph separation procedures with the astronomical epicycles (i.e., the absurd trajectories that had been invented to maintain the geocentric theory before the time of Copernicus and Galilei). To assess baseflow, direct measurement is generally impossible, because aquifer-river exchanges are usually continuous processes that take place all along the stream network. Proxy approaches involving chemical tracer-based procedures are efficient but need chemical data and involve their load of assumptions. Most approaches rely on solving an inverse problem, i.e, reckoning the quantitative causes (here baseflow and quickflow) of an observed physical phenomenon-total runoff. This procedure is very common in hydrology and it is reasonably feasible when the variable can be measured and a calibration procedure can be implemented; but here again, the non-measurable character of baseflow renders the question difficult. It is perhaps impossible to propose a physically based baseflow separation procedure (just because of the multiplicity of flow paths that make the procedure fundamentally equifinal), and we will not argue on this point. But we believe that even the imperfect conceptual-mathematical-empirical methods in use could receive an unarbitrary, impartial, repeatable parameterization that could be used as a general-purpose study tool over large catchment sets.

Sign up for access to the world's latest research.

checkGet notified about relevant papers

checkSave papers to use in your research

checkJoin the discussion with peers

checkTrack your impact