Towards The Quantification Of The Historical And Future Water Resources Of The Limpopo River
- Authors: Kapangaziwiri, Evison , Kahinda, Jean-Marc M , Oosthuizen, Nadia , Mvandaba, Vuyelwa , Hobbs, Philip , Hughes, Denis A
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , report
- Identifier: http://hdl.handle.net/10962/438349 , vital:73453 , ISBN 978-0-6392-0303-4 , https://wrcwebsite.azurewebsites.net/wp-content/uploads/mdocs/2439_final.pdf
- Description: The complexity of current water resource management poses many challenges. Wa-ter managers must solve a range of interrelated dilemmas – such as balancing quan-tity and quality, mitigating the effects of flooding and drought, and maintaining bio-diversity, ecological functions, and services. Sustainable water resource manage-ment, planning, and development requires reliable quantification of the amount, distribution, and quality of water within river basins. With the demand for water resources rapidly growing across the globe, there is also an urgent need for accu-rate monitoring, forecasting and simulation of hydrologic variables – especially in major (often transboundary) river basins such as the Limpopo – not only for optimal water resources management but more compellingly, also for water security, food security, power generation, and economic development. However, the available data are frequently far from sufficient – in terms of availability, accuracy, and spa-tial/temporal resolution – for the understanding of both natural and anthropogenic processes (and their complex linkages) in a river basin. Such challenges also make it very difficult to use the data for the practical application of estimation of water resources availability.
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- Date Issued: 2021
Understanding and quantifying channel transmission loss processes in the Limpopo River Basin
- Authors: Mvandaba, Vuyelwa
- Date: 2018
- Subjects: Water-supply -- Management , Water-supply -- Limpopo River Watershed , Alluvium -- Limpopo River Watershed , Streamflow -- Limpopo River Watershed
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63797 , vital:28490
- Description: 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. A review of previous hydrological studies conducted in the Limpopo River Basin has revealed a gap in the understanding of surface water-groundwater interactions, particularly channel transmission loss processes. These earlier studies, focused largely on the Limpopo River’s main stem, have attributed the existence of these streamflow losses to the presence of significant alluvial aquifers and indicated that the losses account for about 30 percent (or 1000 Mm3 a-1) of the basin’s water balance. The work conducted in this dissertation reports on the delineation of alluvial aquifers across three sub-basins of the Limpopo River Basin namely, the Mokolo (South Africa), Motloutse (Botswana) and Mzingwane (Zimbabwe) sub-basins and the estimation of potential channel transmission losses based on the alluvial aquifer properties. Additionally, an assessment of the different approaches that can be applied to simulate these channel transmission losses in the Pitman Model is presented. To delineate alluvial aquifers, general land cover classes including alluvial aquifers were produced from Landsat-8 imagery through image classification. The areal extent of the delineated alluvial aquifers was calculated using ArcMap 10.3. To quantify channel transmission losses and determine the effects on regional water resources, three approaches using the Pitman model were applied. The three approaches include 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 were able to simulate channel transmission losses, although with differing magnitudes. Observed monthly flow data were used to as a means of validating loss simulations however for each sub-basin, medium and low flows were over-simulated which accounts for water uses that were inefficiently represented due to lack of data. Knowledge of the structure of the transmission loss function dictates that it is better at representing the dynamics of channel transmission losses, as it takes into account the contribution of losses to groundwater recharge whereas the other two functions simply store water and release it back to the channel. Overall, the hydrological modelling results demonstrate the potential of each approach in reproducing the dynamics of channel transmission losses between channel and alluvial aquifer within an existing sub-basin scale hydrological model. It is believed that better quantification of losses and more efficient qualitative determination of the function which best represents transmission losses, can be attained with more reliable observed data. In conclusion, a study of this nature can be beneficial to water resource estimation programmes as it highlights the uncertainties related with quantifying channel transmission loss processes in a semi-arid environment.
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- Date Issued: 2018