9 research outputs found
Parameter and input data uncertainty estimation for the assessment of water resources in two sub-basins of the Limpopo River Basin
The demand for water resources is rapidly growing, placing more strain on
access to water and its management. In order to appropriately manage water
resources, there is a need to accurately quantify available water resources.
Unfortunately, the data required for such assessment are frequently far from
sufficient in terms of availability and quality, especially in southern
Africa. In this study, the uncertainty related to the estimation of water
resources of two sub-basins of the Limpopo River Basin – the Mogalakwena in
South Africa and the Shashe shared between Botswana and Zimbabwe – is
assessed. Input data (and model parameters) are significant sources of
uncertainty that should be quantified. In southern Africa water use data are
among the most unreliable sources of model input data because available
databases generally consist of only licensed information and actual use is
generally unknown. The study assesses how these uncertainties impact the
estimation of surface water resources of the sub-basins. Data on farm
reservoirs and irrigated areas from various sources were collected and used
to run the model. Many farm dams and large irrigation areas are located in
the upper parts of the Mogalakwena sub-basin. Results indicate that water use
uncertainty is small. Nevertheless, the medium to low flows are clearly
impacted. The simulated mean monthly flows at the outlet of the Mogalakwena
sub-basin were between 22.62 and 24.68 Mm3 per month when
incorporating only the uncertainty related to the main physical runoff
generating parameters. The range of total predictive uncertainty of the model
increased to between 22.15 and 24.99 Mm3 when water use data
such as small farm and large reservoirs and irrigation were included. For the
Shashe sub-basin incorporating only uncertainty related to the main runoff
parameters resulted in mean monthly flows between 11.66 and 14.54 Mm3. The range of predictive uncertainty changed to between 11.66
and 17.72 Mm3 after the uncertainty in water use information
was added
Modelling of channel transmission loss processes in semi-arid catchments of southern Africa using the Pitman Model
Water availability is one of the major societal issues
facing the world. The ability to understand and quantify the impact of key
hydrological processes, on the availability of water resources, is therefore
integral to ensuring equitable and sustainable resource management. Channel
transmission losses are an under-researched hydrological process that
affects resource availability in many semi-arid regions such as the Limpopo
River Basin in southern Africa, where the loss processes amount to
approximately 30 % of the water balance. To improve the understanding
of these loss processes and test the capability of modelling routines, three
approaches using the Pitman model are applied to selected alluvial aquifer
environments. The three approaches are an explicit transmission loss
function, the use of a wetland function to represent channel-floodplain
storage exchanges and the use of a dummy reservoir to represent floodplain
storage and evapotranspiration losses. Results indicate that all three
approaches are able to simulate channel transmission losses with differing
impacts on the regional flows. A determination of which method best
represents the channel transmission losses process requires further testing
in a study area that has reliable observed historical records