Modelling water demand for residential households by segregating indoor and outdoor uses

Knox, Ashley Jade (2020-03)

Thesis (MEng)--Stellenbosch University, 2020.


ENGLISH ABSTRACT: The ability of municipalities to deliver a sustainable supply of water to South African customers has become a major problem. Water scarcity is a profound challenge facing most countries worldwide that will continue to escalate without intervention. The need for proper infrastructure planning, effective demand management policies, climate change adaption strategies and the development of alternative water sources, is of critical importance. A key input to achieving these tasks, is the ability to provide accurate estimates of the current and future water demands. The residential water demand is a major component of the urban water use profile with a large water saving potential. Water restriction campaigns often target non-essential, outdoor uses which often account for a large portion of household consumption, especially during the summer months. Guidelines commonly used in South Africa are relatively insensitive to important parameters that influence residential demand and they do not account for seasonal variation. More advanced methods have been developed, such as end-use models, to forecast detailed end-use demand patterns, but are often complex and require extensive input datasets. As part of this study, a model was constructed to estimate the water demand for residential households on a monthly basis, at a reasonable level of accuracy. An attempt was made to incorporate the important influential factors, including relatively few inputs and requiring data that can be sourced fairly easily. The concept of the demand model was to estimate the indoor and outdoor components of household consumption separately. An extensive review of available literature and research papers was done in order to identify and select the most critical factors to include in the model. Household size was found to have the greatest influence on indoor consumption. The surface area of the garden and swimming pool, crop type and climatic variables were identified as important factors affecting outdoor demand. The model could offer insight into the seasonal patterns of household demand and provide a basis for future work on the conservation potential of household water use. An evaluation procedure was conducted by applying the proposed demand model to existing households and comparing the modelled results to the actual consumption. A total of 1 055 households were selected from gated communities in the Western Cape and Gauteng for analysis. Where site data was not available to populate the input parameters, information sourced from previous studies and relevant literature references was used. The monthly meter readings were obtained for each study site and compared to the demands estimated by the model. The model provided reasonably accurate results for 6 out of the 10 study sites, with an accuracy of above 80% for predicting the AADD. This method could be valuable for planning future housing developments and sizing water infrastructure.


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