Climate Change and Its Impacts on Streamflow: WRF and SCE-Optimized SWAT Models - Data Assimilation for Atmospheric, Oceanic and Hydrologic Applications - page 405

climate models resulted in very different projections of future runoff change, such
as in Australia, South America and Southern Africa. The study recognized the
uncertainties that exist amongst the climate projections of various GCMs. Although
this study highlighted uncertainties on a global scale, impact studies over regions
like Africa are even more difficult due to lack of sufficient technological resources
and under-developed scientific research compared to many other parts of the world
( Washington et al. 2006 ).
Some hydrological research studies over the Okavango River basin and
Okavango Delta have been made. The most comprehensive study was conducted
within the EU WERRD project (Water and Ecosystem Resources in Regional
Development). The general objective of this project was to increase understanding
of livelihoods, the environment and policies relating to international river basins. In
this case, the project refers to the Okavango River Basin and was being designed by
many researchers from Botswana, UK, Namibia, South Africa and Sweden, funded
by the European Union. As a part of this project, Andersson et al. ( 2006 ) applied
scenario modelling as a tool for integrated water resource management over the
Okavango River basin. The Pitman hydrological model ( Pitman 1973 ) was used to
assess the impact of various climate change scenarios on downstream river flow.
Pitman model of the river basin was applied to both present day historical
conditions and future climate change scenarios to assess the impact on river
flows. Four GCMs (HadCM3, CCSR/NIES, CCCma and GFDL) with present day
conditions and future A2 IPCC emission scenario were applied in the study. Their
results showed that there was considerable uncertainty about the magnitude and
direction of any future discharge response associated with both the GCM and the
IPCC emission scenarios. Results of the study showed that the modeled experiments
indicated a reduction in future flow after about 2050 for both the A2 and B2 GHG
scenarios that increases over time. This is seen in Fig. 17.2 which shows the mean
monthly flow at a particular station (Mukwe) in the Okavango River basin that was
simulated by the hydrological model used in this study. The key conclusion from the
study was that different GCMs predicted future conditions in the Okavango Basin
ranging from drier than present to wetter than present and there are differences
in both degree of change and direction of change between the Okavango river
catchment area and the Okavango Delta.
In a related hydrological modelling study of the Okavango Delta, Murray-
Hudson et al. ( 2006 ) applied a mathematical model to assess the impacts of changing
hydrological inputs on the flooding in the delta. The assessment of effects of
possible future changes (2020-2050) on the hydrological characteristics of the
Okavango Delta was done by running a hydrological model of the Okavango Delta
with discharge inputs from the Pitman model of the river basin. Three different
GCMs (HadCM3, CCC and GFDL) with the future A2 IPCC emission scenario
were used to drive the hydrological model. The GCMs produced a wide spectrum of
possible future conditions in the Delta as shown in Fig. 17.3 . The authors concluded
that there was a large uncertainty about future climatic conditions and the modeled
effects of climatic variation on the hydrology of the Delta. Figure 17.3 shows the
different flood plain classes categorized according to Permanent Flooded (PF),