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Rainwater harvesting (RWH) is perhaps the most ancient practice to meet water supply needs. It has received renewed attention since the 1970s as a productive water source, water savings and conservation means, and sustainable development tool. In RWH, it is important to know how much water can be harvested at a given location from a given catchment size, whether the harvested water meets the intended water quality, whether the RWH system is economically viable and whether the state regulations favor the RWH. Furthermore, the selected RWH system should be suitable to local rainfall and field conditions, downstream impacts, and socio-economic and cultural characteristics. In this regard, this paper provides an overview of the special issue on "Rainwater Harvesting: Quantity, Quality, Economics and State Regulations". The selected papers cover a wide range of issues that are relevant to RWH such as regionalization of design curves, use of spatial technology, urban agriculture, arid-region water supply, multi criteria analysis and application of artificial neural networks. [ABSTRACT FROM AUTHOR]

Rainwater tanks are increasingly being implemented as part of the integrated urban water management paradigm where all sources of water, including potable, stormwater and recycled, are considered eligible to contribute to the urban water supply. Over the last decade or so, there has been a rapid uptake of rainwater tank systems in urban areas, especially in Australian cities, encouraged through financial incentives, but more importantly, from change in residential building codes effectively mandating the installation of rainwater tanks. Homes with rainwater tanks in Australian cities have increased from 15% to 28% over six years to 2013. These building codes specify certain rainwater tank specifications to achieve a stated rainwater use, and hence potable water savings. These specifications include minimum rainwater tank size, minimum connected roof area, plumbing for internal supply for toilets and washing machines, and external supply for garden watering. These expected potable water savings from households are often factored into regional strategic water planning objectives. Hence if rainwater tanks do not deliver the expected saving due to sub-standard installation and/or poor maintenance, it will have an adverse impact on the regional water plan in the longer term. In this paper, a methodology to assess the effectiveness of a government rainwater tank policy in achieving predicted potable water savings is described and illustrated with a case study from South East Queensland, Australia. It is anticipated that water professionals across the globe should be able to use the same methodology to assess the effectiveness of similar rainwater policies, or indeed any other distributed water saving policy, in their local planning communities. [ABSTRACT FROM AUTHOR]

Rainwater harvesting (RWH) has become a popular water saving and conservation means across the globe. In many cities, a pre-determined rainwater tank size is generally selected without a detail water balance modelling at the location on interest. However, to achieve maximum benefit from a RWH system at a given location, it is desirable to design the system based on the site specific conditions (e.g. local rainfall and loss characteristics) and other relevant design parameters. There have been limited studies on regionalization of RWH system, which can account for the spatial variability in rainfall, loss and water demand characteristics over a given region to provide site-specific design of RWH system. This paper presents a RWH regionalization approach to develop a set of design curves, which assist in the selection of an adequate RWH system at a given location. We use rainfall data from 159 rain gauges across the Greater Sydney region in Australia to develop and test the proposed regionalization approach. It has been found that there is a significant variation in rainfall characteristics across Greater Sydney region and that a common tank size across this region does not present an adequate solution. It has been found that a 5 kL tank can achieve a reliability (i.e. percentage of days the RWH can meet the given demand) of 31–93% for four people depending on the location in the Greater Sydney region and the types of water use. The developed regional design curves could result in increased water savings across Greater Sydney. The proposed regionalization approach can be adapted to other cities across Australia and the world which present a high rainfall gradient. • Water savings by rainwater harvesting at 159 locations in Sydney are evaluated. • Reliability of a rainwater tank is moderately correlated with mean annual rainfall. • A set of design curves is developed for Sydney to enhance rainwater harvesting. [ABSTRACT FROM AUTHOR]