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Impact of Climate Change on the Design Criteria for Rainwater Harvesting Systems in Western Australia

Author(s): Neil Coles; Chun Woo Baek

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Keywords: Rainwater Harvesting; Reliability; RAINTANK2 model; Climate Change

Abstract: Rainwater harvesting systems have become an increasingly significant water resource due to recent declining rainfall trends attributed to climate change in arid and semi-arid areas in Western Australia. In particular, roof rainwater collecting systems provide an important alternative sustainable water resource for small communities that do not have access to the comprehensive water supply scheme. Due to declining and concentrated rainfall patterns in the south-western arid and semi-arid areas of Western Australia, the design of major components of roof rainwater collecting systems is a key issue in their efficiency and cost. Reliability evaluation of the system may change the results of tank design and the relative reliability of the system. Therefore, determination of what constitutes failure and the target reliability of the system is highly critical in the design of a roof rainwater collecting system. In this study, the potential of using roof rainwater harvesting systems in arid and semi-arid areas in the South-West region of Western Australia is presented. The system reliability is calculated for 363 locations depending on three modelling time intervals and five definitions of reliability; with a total of 12 scenarios defined. Sixty years of rainfall data is utilised in a water balance simulation, with the rainfall data of the most recent 20 years evaluated separately to account for recent climate variability. Calculated system reliability has been analysed to suggest the best design options and roof-raintank combinations for the South-West region. A weekly modelling time interval and monthly period-based estimation of reliability were determined to be the best option for the SouthWest region. The size of the raintank, based on the target reliability was determined using the modified RAINTANK2 model to demonstrate the potential distribution and appropriate designs for roof rainwater harvesting systems in semi-arid and arid regions.


Year: 2012

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