The
science that underpins our knowledge and understanding of Isotope-Based Hydrograph separation (IHS) has
gained grounds, over the last few decades, in the identification of streamflow
sources. However, challenges still exist in identifying appropriate tracers and
the right combination of end-members for the IHS process. In a two-component IHS analysis, the application of the dual isotopes tracers, δ18O and (or) δ2H,
is regarded as the simplest method. We
undertook an IHS study within a nested system of eight Prairie watersheds
located in South central Manitoba, Canada. The work evaluated about 17,000
results emanating from the application of a combination of two potential
tracers (δ18O and δ2H)
and eight each of potential “old” and “new” water end-members in a
two-component IHS process. The outcome showed occurrences of many
mathematically possible but hydrologically unacceptable IHS results. The
observation was particularly predominant within relatively larger perennial
sub-catchments of the watershed. It is also shown that inter-site sub-catchment
isotopic end-member transferability is possible within watersheds of similar
physio-hydrographic characteristics. We suggest that a careful evaluation of
the physio-hydrographic characteristics of catchments be considered in IHS
studies in addition to the recommended guidelines in the selection of tracers
and end-members.
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