M.Ing. (Civil Engineering Science) / In recent years, there has been an international trend towards installing rainwater tanks in an attempt to save water. However, there are no clear guidelines for determining the optimal size of such a tank in South Africa. This study investigates the possibility of simplifying the process of sizing a rainwater tank for optimal results. It utilises daily data from four rainfall stations, namely Kimberley, Mossel Bay, Punda Maria and Rustenburg, obtained from the South African Weather Services. The water use is considered to be for indoor purposes only, therefore assuming a constant daily demand to be extracted from the tank. The required size of a rainwater tank is influenced by the MAP, the area of the roof draining into the tank, the water demand (both the average demand and seasonal variations), the desired reliability of supply, and the rainfall patterns. The first step in simplifying the process is to consolidate the above variables. The tank volume is expressed as the number of days it could supply the average daily water demand. Another variable is created which provides the ratio of the total water volume which could theoretically be harvested from the roof in an average year, to the total water demand, from the tank, for a year. This has the effect of consolidating the MAP, the roof area, the water demand and the tank volume into two variables only and eliminates the need to consider numerous demand values. Using simulations over 16 years for each location, the relationships between these variables were determined to ensure 90%, 95% and 98% assurance of supply.

The utilisation of rainwater tanks and bore wells are very common in many parts of rural Australia and Papua New Guinea. In Australia, on-site collection and storage of potable water for domestic use is carried out by approximately 30.4 percent of the rural population while 90% of the population in Papua New Guinea access water from on-site collection and storage of potable water. Few studies have monitored the quality of such water supplies on a seasonal and event associated basis. The aim of this study was to evaluate the microbiological and physio-chemical properties of the on-site domestic water supply systems and various factors that may influence characteristics of the water. It aimed to evaluate the relationship of microbiological and physio-chemical characteristics in the water supply systems. 14 rainwater tanks, 4 bore well and 10 reticulated water supply sites in Hawkesbury District, NSW Australia were investigated. Characteristics of the sites physical situation and natural environmental condition were considered to be similar to on-site water supply situations in Papua New Guinea. The results and techniques of the study will be used as a model in Papua New Guinea in the assessment of water quality issues. As the study showed that the quality of water in rainwater tanks was below WHO guideline recommendations on numerous instances, it was proposed that water treatment and maintaining the cleanliness of roof catchments, gutters and tanks should be addressed for domestic use systems. A protocol for sampling, assessment and data interpretation of faecal indicator bacteria populations in domestic catchment supply systems was developed and demonstrated / Master of Science (Hons)