A case study on reliability, water demand and economic analysis of rainwater harvesting in Australian capital cities

This paper presents reliability, water demand and economic analysis of rainwater harvesting (RWH) systems for eight Australian capital cities (Adelaide, Brisbane, Canberra, Darwin, Hobart, Melbourne, Perth and Sydney). A Python-based tool is developed based on a daily water balance modelling approach, which uses input data such as daily rainfall, roof area, overflow losses, daily water demand and first flush. Ten different tank volumes are considered (1, 3, 5, 10, 15, 20, 30, 50, 75 and 100 m3). It is found that for a large roof area and tank size, the reliability of RWH systems for toilet and laundry use is high, in the range of 80–100%. However, the reliability for irrigation use is highly variable across all the locations. For combined use, Adelaide shows the smallest reliability (38–49%), while Hobart demonstrates the highest reliability (61–77%). Furthermore, economic analysis demonstrates that in a few cases, benefit–cost ratio values greater than one can be achieved for the RWH systems. The findings of this study will help the Australian Federal Government to enhance RWH policy, programs and subsidy levels considering climate-sensitive inputs in the respective cities

Evaluation of rainwater harvesting systems in three major cities of New South Wales

Rainwater harvesting (RWH) systems are becoming more popular to reduce pressure on mains water as well as to serve as a sole freshwater supply system in rural areas. Australia is a large continent with highly variable rainfall and hence performance of a RWH system varies from location to location. This paper presents reliability and water-saving potential of a RWH system in three major cities namely Sydney, Newcastle and Wollongong of New South Wales (NSW) State of Australia. A python-based daily water balance model is built to analyse the performance of a RWH system, which uses rainfall, loss, water demand and roof catchment data. To enable selection of ideal rainwater tank size for the selected locations, three different water uses (toilet and laundry, irrigation, and combined use) and five tank sizes (1, 5, 10, 20 and 30 kL) are considered. It is found that the rainwater tank size is influenced by roof area, number of users, water demand and rainfall characteristics. This study will help in decision-making regarding implementation of a RWH system in these Australian cities. This research also contributes towards achieving water related sustainable development goals (SDG)

Assessing the impacts of climate change on rainwater harvesting : a case study for eight Australian capital cities

Due to climate change, freshwater supply will be limited at many locations around the globe. Rainwater harvesting (RWH) has emerged as an alternative and sustainable freshwater source. In this study, the impacts of climate change on water saving as well as the reliability of a RWH system are investigated using data from eight Australian capital cities. Both historical and projected rainfall data were incorporated into a daily water balance model to evaluate the performance of a RWH system in relation to its reliability, water savings and scarcity. Indoor (toilet and laundry), outdoor (irrigation) and combined (indoor plus outdoor) water demands were considered for a 5 m(3) tank size. It has been found that in the future period, the water savings and reliability of a RWH system will reduce slightly across the selected cities. Different capital cities of Australia will experience different level of performance for a RWH system depending on their locations, water uses and seasons. The findings of this study will be useful to water authorities and policy makers to plan for a sustainable RWH system under changing climate conditions

Application of GIS in rainwater harvesting research : a scoping review

The spatial and temporal variability of quantity and quality of water are important aspects of water resources management. Water demand has been increasing across the globe, but the fresh water supply is limited. Rainwater harvesting (RWH) systems are increasingly being embraced as an alternative freshwater source. This study reviews the dynamics of global research on RWH that utilises geographic information systems (GIS). It is found that the interest and use of RWH utilising GIS have increased over the recent years. However, the full potential of GIS in large scale RWH is yet to be untapped. We make recommendations for future research on RWH based on GIS. This includes new software and model development that links RWH with GIS to plan and design large scale RWH and automated building footprint extraction for estimating RWH potential. GIS can play a bigger role in achieving Sustainable Development Goals (SDGs) by incorporating GIS with RWH since GIS can handle large spatial data efficiently, which can help in locating areas that are suitable for rainwater harvesting

Potential of rainwater harvesting in Greater Sydney : a proposed educational tool for Sydney school children

Rainwater harvesting (RWH) is recognised as a sustainable means to overcome water scarcity and cope with the climate change and variability. RWH can be an important supplementary source of water in parts of the world like Sydney in Australia where water demand is as high as 300 litres per person per day on average, which is very high compared to many developing countries. Due to higher water demand and environmental awareness, RWH systems have become very popular in Sydney in recent years. This study explores how rainwater can best be harvested across Sydney and how a school education tool can be developed to create water conservation awareness among school students in Sydney. In the data analysis, stations were used covering three study periods, 30 years (1986-2015), 50 years (1966-2015), and 70 years (1946-2015). Spatial and temporal analysis is done to demonstrate rainfall variability and potential of rainwater harvesting in Greater Sydney. This paper proposes an educational tool to be developed that can be used to identify the locations where more water can be saved within Sydney. Further research is continued to develop this tool in near future

Potential of rainwater harvesting in Greater Sydney : a proposed educational tool for Sydney school children

Rainwater harvesting (RWH) is recognised as a sustainable means to overcome water scarcity and cope with the climate change and variability. RWH can be an important supplementary source of water in parts of the world like Sydney in Australia where water demand is as high as 300 litres per person per day on average, which is very high compared to many developing countries. Due to higher water demand and environmental awareness, RWH systems have become very popular in Sydney in recent years. This study explores how rainwater can best be harvested across Sydney and how a school education tool can be developed to create water conservation awareness among school students in Sydney. In the data analysis, stations were used covering three study periods, 30 years (1986-2015), 50 years (1966-2015), and 70 years (1946-2015). Spatial and temporal analysis is done to demonstrate rainfall variability and potential of rainwater harvesting in Greater Sydney. This paper proposes an educational tool to be developed that can be used to identify the locations where more water can be saved within Sydney. Further research is continued to develop this tool in near future

Rainwater harvesting in Australia using an Australia-wide model : a preliminary analysis

As the world's population is increasing, so the demand for fresh water is augmenting simultaneously. Groundwater resources are being utilized faster than they can be recharged, and surface water is becoming limited due to higher water use. Rainwater harvesting (RWH) is recognised as a sustainable means to overcome water scarcity and cope with the climate change and variability. RWH can be an important supplementary source of water in parts of the world like Australia where water demand is very high compared to many developing countries. Furthermore, Australia is one of driest continents and has the most variable rainfall with long periods of intense droughts and occasional devastating floods. Due to the higher water demand and environmental awareness, RWH systems have become popular in Australia in recent years. This study explores how rainwater can be harvested across Australia. In this study, daily rainfall stations covering three study periods, such as 30 years (1986-2015), 50 years (1966-2015), and 70 years (1946-2015) are used. Spatial analysis is carried out to demonstrate rainfall variability and the potential of rainwater harvesting in Australia. The ongoing study is aimed to develop a model to design an optimum RWH system at any arbitrary location in Australia

Development of a windows-based tool to model RWH system

Water scarcity has become a global issue in recent years. Recently, water scarcity has been further exasperated due to climate change. Rainwater harvesting (RWH) technique has been receiving great attention as an alternative water source due to rising water scarcity throughout the world. This paper presents the development of a python-based daily water balance tool to analyse the RWH system performance and optimise a potential rainwater tank size. The developed tool performs three different tasks, namely, reliability, sensitivity, and economic analyses. In the first step, the tool calculates the reliability of a particular size tank, connected with a particular roof area to fulfill the expected rainwater demand. Secondly, three distinct years (climate conditions) are considered in the sensitivity analysis to account for climate variability: a dry year, an average year, and a wet year. Finally, the tool calculates net present values (NPV) and benefit-cost ratios (BCR) to assess the cost-effectiveness of the proposed rainwater tank system. The developed tool is user-friendly that will make decision-making process for end-users simple, effective, and informed. It will facilitate the end-users to perform a cost-benefit assessment and eventually will encourage many people/organizations to optimise and install a feasible RWH system