Unpacking some of the linkages between uncertainties in observational
data and the simulation of different hydrological processes using the
Pitman model in the data scarce Zambezi River basin.
The main objective of this study was to use an uncertainty version of a
widely used monthly time step, semi-distributed model (the Pitman model)
to explore the equifinalities in the way in which the main hydrological
processes are simulated and any identifiable linkages with uncertainties
in the available observational data. The study area is the Zambezi River
basin and 18 gauged sub-basins have been included in the analyses.
Unfortunately, it is not generally possible to quantify some of the
observational uncertainties in such a data scarce area and mostly we are
limited to identifying where these data are clearly deficient (i.e.
erroneous or non-representative). The overall conclusion is that the
equifinalities in the model are hugely dominant in terms of the
uncertainties in the relative occurrence of different runoff generating
processes, although water use uncertainties in the semi-arid parts of
the basin can contribute to these uncertainties. The identification of
landscape features that suggest the occurrence of saturation excess
surface runoff provides some information to constrain the model.
Improved independent estimates of groundwater recharge is also
identified as a key source of observational data that would help a great
deal in constraining the model parameter space and therefore reducing
some of the model equifinality.