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dc.contributor.authorBardsley, W. Earlen_NZ
dc.date.accessioned2018-08-21T23:28:56Z
dc.date.available2018en_NZ
dc.date.available2018-08-21T23:28:56Z
dc.date.issued2018en_NZ
dc.identifier.citationBardsley, W. E. (2018). Transit time distributions are not L-shaped. Journal of Hydrology (NZ), 57(1), 35–40.en
dc.identifier.issn0022-1708en_NZ
dc.identifier.urihttps://hdl.handle.net/10289/12032
dc.description.abstractA probability density function f(t) with origin at t = 0 is defined here as being ‘L-shaped’if f ʹ(t) ≤ 0 for t ≥ 0. L-shaped probability density functions, such as exponential distributions, are often employed as transit time distributions in hydrological modelling. However, the use of L-shaped transit time distributions implies including tracer particles that were already present at the observation point at time t = 0. These passive particles have no transit history by definition because ‘transit’ implies some history of movement of a particle through a hydrological system, however small that movement may be. That is, the particle must have reached the observation point by moving to it for some non-zero time and over some non-zero distance through a hydrological system such as a catchment or aquifer. By this argument, particles that happen to be already at the observation point at time t = 0 represent background noise. The distinction between the inclusion or not of particles already at the observation point might seem pedantic but does have an important implication: if transit time distributions in the hydrological environment are defined to not include non-transiting particles, they must have the property f ( 0) = 0. This negates the possibility of L-shaped transit time distributions. The exclusion of non-transiting particles also has the implication that transit time distributions must have at least one mode at t > 0, which may or may not be identifiable from field measurements.
dc.format.mimetypeapplication/pdf
dc.language.isoen
dc.publisherNew Zealand Hydrological Societyen_NZ
dc.rights© New Zealand Hydrological Society (2018). Used with permission
dc.subjecttransit time distributionen_NZ
dc.subjectfirst passage timesen_NZ
dc.subjectabsorbing barrieren_NZ
dc.subjectreflecting barrieren_NZ
dc.titleTransit time distributions are not L-shapeden_NZ
dc.typeJournal Article
dc.relation.isPartOfJournal of Hydrology (NZ)en_NZ
pubs.begin-page35
pubs.elements-id226445
pubs.end-page40
pubs.issue1en_NZ
pubs.volume57en_NZ


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