Climate change is a highly contentious topic in the modern world. There is much evidence to indicate that climatic shifts and extreme weather anomalies are taking place globally, in some places more than others. This paper presents the findings on research to determine whether shifts in seasonal rainfall patterns are indeed already visible in historical rainfall data in the Western Cape of South Africa. The paper aims to provide some baseline information which can stimulate further research in this field. Different analytical methods were formulated to investigate the relationships between daily rainfall indices over a set timescale. Data was collected from the South African Weather Service (SAWS) in order to accumulate 20 rainfall stations, each with at least 100 years of historical daily rainfall data. Statistical analysis, linear trend line distributions, time lag comparisons, cumulative distributions, moving average plots and autocorrelation relationships were applied to the data. The results of the analysis indicated that (1) the rainfall season undergoes fluctuations of wetter and drier years (approximately 20-year cycles), (2) the South Coast region exhibits a shift towards a longer rainfall season, and in contrast the Mediterranean region is shifting to a shorter rainfall season when linear trend lines were analysed, and (3) the moving average plots showed only isolated seasonal shifts at the boundary months.

Long-term rainfall data with good spatial and temporal distribution is essential for all climate-related analyses. The availability of observed rainfall data has become increasingly problematic over the years due to a limited and deteriorating rainfall station network, occasioned by limited reporting and/or quality control of rainfall and, in some cases, closure of these stations. Remotely sensed satellite-based rainfall data sets offer an alternative source of information. In this study, daily and monthly rainfall data derived from Climate Hazards Group InfraRed Precipitation (CHIRPS) is compared with observed rainfall data from 46 stations evenly distributed across South Africa. Various metrics, based on a pairwise comparison between the observed and CHIRPS data, were applied to evaluate CHIRPS performance in the estimation of daily and monthly rainfall. The results show that CHIRPS data correlate well with observed monthly rainfall data for all stations used, having an average coefficient of determination of 0.6 and bias of 0.95. This study concludes that monthly CHIRPS data corresponds well, with good precision and relatively little bias when compared to observed monthly rainfall data, and can therefore be considered for use in conjunction with observed rainfall data where no or limited data is available in South Africa for hydrological analysis.

As water demands continue to grow, South Africa is starting to consider seawater desalination as a potential future supply source, and it is currently being investigated at a feasibility level in a number of coastal cities, including Cape Town. Desalination is different to conventional surface and groundwater supply sources in that it is climate-resilient, having an assurance of supply of essentially 100 percent. However, the increased reliability comes at a great cost. This paper presents a methodology developed for modelling a proposed desalination plant as an integrated component of the Western Cape Water Supply System, in order to optimise system operating rules and cost. The modelling entailed short-term and long-term system analyses in the Water Resources Yield Model and Water Resources Planning Model, and estimation of first-order capital and operating costs in order to calculate and compare Unit Reference Values. The maximum increase in yield was found to occur when the seawater desalination plant is used as a base supply, operational all the time. There was little benefit, in terms of system yield, in using the desalination plant as an emergency supply source only. Unit reference values for the desalination plant decrease as the percentage supply from the plant increases, meaning that the lowest possible cost per cubic metre of water supplied is when the desalination plant is used as a base supply. It was also apparent that the unit reference values decrease with an increase in desalination plant capacity, suggesting that, from an economic perspective, the optimal solution would be to have one large desalination plant operational immediately.

Municipalities need to develop Water Services Development Plans (WSDPs) as a first requirement in their budgetary process, and need to be made aware of the options that are available to provide more than basic services. While 25ℓ/person•d has been set as the minimum basic water supply and while many consumers receive far in excess of this amount, there are areas of the country where water of acceptable quality is not available for household use. However, in many areas adequate quantities of saline water may be, or are, readily available. This is especially the case for coastal cities and towns. The cost of treating water is only part of the total cost of making drinking water available to the consumer. This together with the fact that membrane technology is becoming more affordable and that energy can be recovered, makes the desalination of water viable for domestic purposes. A desk study, funded by the Department Water Affairs and Forestry and managed by the Water Research Commission, was undertaken to identify treatment options for desalinating seawater from both the Indian and Atlantic oceans or brackish water from boreholes. The specific objectives of the project were to compile a Guide on the technologies that can be implemented in South Africa to treat saline water to drinking water standards, to identify the pretreatment that is necessary, and to present guidelines on operational, maintenance, management and environmental aspects relevant to the selection and use of these technologies. An important aspect was also to quantify the capital and operating costs for planning purposes of the different components needed to successfully bring the water to the accepted standards for potable and domestic use. Of particular importance for the South African application was to identify the level of skills required for daily operation of the desalination plants, the level of skills required to provide technical backup and advice, and to identify and advise on the competencies, training needs and capacity building required at operator and management levels. Lastly, the relevant local environmental legislations governing desalination were also identified.

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