Browsing by Author "Braune, Erika Gertrud"
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- ItemA stochastic, daily time-step model for the conjunctive use of surface water, groundwater, desalination and water reclamation for municipalities(Stellenbosch : Stellenbosch University, 2020-03) Braune, Erika Gertrud; Du Plessis, J. A.; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.ENGLISH ABSTRACT: South Africa has a broadly-developed water infrastructure based mainly on surface water, localised groundwater and occasional desalination as resources. However, the most suitable sites for surface water storage have been utilised and with population growth and economic factors driving the increase in demand, as well as changing climate conditions, it is projected by the Department of Water and Sanitation that South Africa’s water demand will exceed the available fresh-water by 2025. To mitigate water scarcity, more conjunctive water use solutions need to be investigated. To implement conjunctive management of scarce water resources at a local authority level, a Microsoft Excel model was developed to assess the combined yields of surface water, groundwater and desalinated and reclaimed water, using a daily time step. The model is stochastically driven by synthetically generated streamflow sequences. Monthly streamflow is disaggregated into daily streamflow and a streamflow-rainfall relationship is established to generate corresponding synthetic rainfall sequences. The conventional dam balancing equation, with daily streamflow, is used in the modelling. Groundwater is modelled using a similar approach as the Aquifer Firm Yield Model with the saturated volume fluctuation equation as the stochastic link between rainfall, recharge and water levels. This model is paired with the Cooper-Jacob model and data from Groundwater Resource Assessment Phase 2 project. Desalination and water reclamation are modelled as one source which provides water at 100% assurance of supply at different operational capacity levels over fixed three-monthly time steps. The model evaluates the available yield of the system with water from desalinated sources (including reclaimed) and groundwater used first, according to minimum operational procedures, after which surface water is utilised. A control is built into the model which shuts down the desalination plant if the dam capacity reaches user-defined levels. The model allows for multiple alternative water resources, based on consumer defined input. Additionally, the short-term and long-term assurance of supply is graphically presented which can aid management decisions. An analysis of the historical water supply system is produced while information towards improvement of water management is also provided.