A systems approach to urban water services in the context of integrated energy and water planning: A City of Cape Town case study

Abstract

The City of Cape Town derives the bulk of its present water supply from surface water resources and is the central water service authority for metropolitan consumers. The City is also a provider of bulk water to neighbouring municipalities. An exploration of the energy consumption for water and sanitation services for the City of Cape Town was conducted with an emphasis on water supply augmentation options for the near future (2011-2030). A systems analysis of municipal urban water services was undertaken to examine the energy requirements of supply alternatives and the efficacy of the alternatives in respect of supply availability and reliability. This was achieved using scenario based analysis incorporating a simple additive value function, to obtain a basic performance score, to rank alternatives and facilitate a quantitative comparison. Utilising the Water Evaluation and Planning hydrological modelling tool, a model for urban water services was developed for the City and used to conduct scenario analyses for a representative portfolio of previously identified options. Within the scope of the research objectives, the scenario analyses examines the direct energy consumption for the provision of water services for the City as influenced by external factors such as population growth, surface water runoff variability, available alternatives and the policies that are adopted which ultimately determine the future planning. It is contended that the modelling process presented here integrates energy and water planning for an assessment of water and energy resources required for future growth, and the optimal measures that could be pursued to reconcile the demand for water and the concomitant energy requirements.