Projection of water demand for river basins: case study in the Bloem Water service area, South Africa

摘要

Climate variability and the consequent problems of continuous urbanization threaten water resource availability, particularly in less developed countries such as South Africa. This necessitates the pro-active determination of water needs to comply with the resource availability within a specified future period. Resulting from this is the need for purpose-built management plans and tools to enable water services providers to meet the water demand of the communities it serves. A comprehensive literature study regarding methods for the projection of future water needs has proven that very few of these models have been developed successfully. It also became clear that it is of the utmost importance to accommodate all possible relevant variables in such a model. The variables, to mention a few, are climatological, anthropological, demographic, socio-economic and economic factors, as well as water engineering related factors (e.g. water losses, water leakages etc.). Also very important are the effect of the HIV pandemic on population growth and consequently on water demand. The following actions were seen as important in the development of the model: selection of model structure (e.g. the choice of variables); choice of the functional format (e.g. linear or logarithmic); determining/calculation of the coefficients for the model (regression-analysis); verifying and testing of the model; application of the model; and sharing application methods with the client. The model furthermore has to comply with a variety of factors such as unexpected and extreme temperature changes with high peak demands, water tariffs, demographic movement, etc. and must be able to reflect reasons for historic water consumption tendencies and project expected water consumption using different predicted values for the relevant variables. The results from this study will put the water services provider in a pro-active position regarding prioritization of refurbishment of existing infrastructure, prioritizing needed capital work (extension of infrastructure), and more importantly, to be in a position to determine realistic tariffs and enable the organization to be managed and operated in an effective way. The study area consists of two river basins of which the water services provider (water board) is Bloem Water.