Applications and methods for rainwater harvesting in the arid zone

Applications and methods for rainwater harvesting in the arid zone

WQRA Summer Student

Water Quality Research Australia summer scholarship student, Chris Smithies, has just completed a 10 week project with CAT. He is an undergraduate in his final year of a double degree in Environmental Management and Business & Technology at Flinders University in Adelaide, SA. His project is titled: ‘Applications and methods of rainwater harvesting in the arid zone’.

The project documented the existing types of rainwater harvesting in arid Australia and explored its potential applications throughout the region as an alternative form of water supply. The project found that the arid zone is predominantly groundwater reliant and that many areas have issues with groundwater quality. It also found that, despite its limitations in the arid zone, rainwater harvesting has potential applications as a supplementary water supply to increase water quality and security. Rainwater harvesting systems also have potential applications for stormwater management and pastoral land rehabilitation.

Chris would like to thank all CAT staff for making his stay in Alice Springs an enjoyable as well as educational one.

Executive Summary of the Rainwater Harvesting Report

Issues with water quality and quantity in Australia’s arid zone necessitate a re-examination of alternative water sources to supplement existing supplies. Most arid zone communities are reliant on groundwater as their primary water source. Groundwater in many parts of the arid zone has a high level of dissolved minerals which exceed the Australian Drinking Water Guidelines for health or aesthetic characteristics. According to reports in 2008 and 2009 by the Northern Territory’s Power and Water corporation, 95% of the 72 remote Indigenous communities managed by Power and Water used groundwater as their main water source and 20 of those communities’ water supplies were shown to contain high concentrations of antimony, arsenic, barium, fluoride, hardness, iron, nitrate, selenium, total dissolved solids, and uranium. This has potential adverse impacts for people that drink the water as well as on the lifespan of infrastructure, fittings and appliances. Groundwater in much of the arid zone also has negligible recharge. Studies in the southern part of the Northern Territory have found groundwater to be 10,000 years old with almost no recharge, with the implication that for management purposes it can be considered an unsustainable resource.
Remoteness and low population densities can also impact on the viability of groundwater as a water source. Technical specialists required for repairs are often located far from where they are required. This adds significantly to operational and maintenance costs of existing water supply systems and leads to delays in water service provision in times of system breakdown.

These factors present opportunities for rainwater harvesting systems to be integrated into existing water supply infrastructure or new infrastructure as an alternative form of supply. Rainwater harvesting in its broadest sense can be defined as the local collection and storage of rainfall through different technologies, for future use to meet the demands of human consumption or human activities. All rainwater harvesting systems are made up of a catchment and storage component. Water supply systems also have a distribution component and depending on the end use of the water, they may also have a treatment component.

This report involved an examination of the different types of existing rainwater harvesting systems throughout the arid zone as well as investigating their possible future applications. Information was collected from a variety of sources including a desktop study, review of existing published and non published literature, numerous interviews with various stakeholders, and a number of site visits to locations with rainwater harvesting infrastructure. Seven case studies of different rainwater harvesting systems throughout the arid zone were compiled as part of the report.

The report found that potential applications of rainwater harvesting are limited to an extent by environmental and economic challenges, but there are also various site specific applications for rainwater systems that can provide significant benefits for arid zone communities. Challenges to further implementation of rainwater harvesting in the arid zone include the low level and variable nature of rainfall combined with high evaporation rates in the region. Though there were no economic comparisons performed in this project, a number of economic constraints to rainwater harvesting in arid Australia were identified, such as the cost of replacing existing infrastructure that is currently designed to suit other water sources and a lack of capacity in some remote areas for residents to manage their own de-centralised form of water supply. Additional management required by service providers may also be a barrier to the further implementation of rainwater harvesting systems.

The research found however, that rainwater harvesting systems are capable of providing stand alone supplies or supplementary water supplies, for potable or non potable use throughout the arid zone. Rainwater harvesting can provide improved water quality over current water sources which may lead to better health outcomes and prolong the lifespan of infrastructure, fittings and appliances. Rainwater is a renewable water source and integrating it into existing arid zone water supply systems will enhance water security and provides an additional water source in times of emergency such as flooding or bushfires. In addition rainwater harvesting systems have important implications for stormwater management, enhancing community landscapes and land rehabilitation throughout the arid zone.

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