Historically, the city of Cape Town has been affected by water shortages and it can be assumed that the situation will be exacerbated in the coming decades by a growing population, economic development and climatic changes as additional stress factors. In order to defuse the situation, the city of Cape Town has commissioned various feasibility studies concerning the implementation of alternative water sources, with as yet unpublished conclusions. Since sustainable water resource planning requires a comprehensive understanding of the water demand, the objective of this study was to predict the future demand by the city of Cape Town by analysing its significant drivers. For this purpose, a linear multiple regression analysis was applied on parameters which influence water demand, namely: population, economy, water losses and water restrictions. In order to establish the linear multiple regression model and its regression coefficients, historical data was used for the period 2001 to 2012. The result of the regression analysis showed that the water demand of the city of Cape Town is only decisively influenced by population and water losses. In addition, the model indicated that a new source would be required by 2021. Thus, water conservation and water supply strategies can be adapted accordingly to ultimately enable a sustainable management of the water sources in the city of Cape Town.