Geoscience Reference
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in the rainfall inputs, the effects of vegetation on the input concentrations, and the spatial variability of
concentrations of water stored in different soil horizons and parts of the catchment. However, at least in
ideal conditions when there is a strong difference between the concentrations observed in rainfalls and the
concentrations of water stored in the catchment before an event, the measured concentrations can be used
in a simple two-component mixing model to differentiate between the contribution to the hydrograph for
an event of the rainfall and the contribution of the water stored in the catchment prior to the event.
Some of the first hydrograph separations of this type were published by Crouzet
et al.
(1970) based on
using tritium derived from atomic testing as a tracer (see also Stewart
et al.
, 2010) and revealed that the
contribution of stored water (often called the “pre-event” or “old” water component) was surprisingly high
(Figure 1.6). This result has been confirmed by many other studies for a wide range of different catchments
Figure 1.6
Hydrograph separation based on the concentration of environmental isotopes (after Sklash, 1990,
with kind permission of Wiley-Blackwell).
