Vulnerability of Water Services in Pacific Island Countries: combining methodologies and judgment

Water services in Pacific Island Countries are particularly vulnerable due to a range of circumstances such as the scale of operation, remoteness of location, financial constraints, cultural complexity and the ability to access technical and other capacity by their administrations. Additionally, the authors argue that comparative assessment of water needs for differing locations is fraught with difficulty because of the combination of systemic complexity, diversity of situations and lack of suitable, consistent and objective data. In these challenging situations, a method for assessment of the vulnerability of water services has been developed on the basis of knowledge and experiences of water professionals, elicited using a structured group interaction known as a Delphi survey. The Delphi survey has been undertaken with a range of stakeholders including panels of experts, funding agencies and local decision makers. Through the Delphi process, key factors contributing to vulnerability have been identified and the output has been used to develop an index methodology. Such an index methodology, similar to the Climate Vulnerability index, has a number of dimensions, variables and appropriate weights expressed within a set of equations. Given quantification of variables, this method can be used to assess the relative vulnerability of water services in Pacific Island Countries. The method used to develop this index could also be applied to other contexts where appropriate

Exploring the need for rainwater tank maintenance: survey, review and simulations

Rainwater tanks are a common feature of the urban landscape in Australia and globally. In Brisbane, Australia, provision of alternative water in new homes is mandatory and to meet this requirement rainwater tanks are considered an important option. The water savings of rainwater tanks can help defer investments in supply infrastructures. An emerging concern is that there is currently no mechanism in place for making sure that the household rainwater collection systems are maintained and in a good condition. In fact, in many locations, there is growing concern about whether the condition of this asset stock is adequate. The paper presents: a synthesis of required basic water tanks maintenance tasks; a short overview of published literature on householder motivations for maintenance; a synthesis of existing information about the condition of tanks, based on literature; simulation model results identifying the relationship between frequency of inspections and the (stationary) proportion of tanks with different types of problems; and the results of a survey to identify judgements about water tank maintenance in the region by professionals and plumbers. The paper concludes that there is a need for collecting more data and that mechanisms need to be in place to ensure the ongoing condition of tanks.</jats:p

Rethinking urban water systems - revisiting concepts in urban wastewater collection and treatment to ensure infrastructure sustainability

Technology and economic development has led to the growth of megacities and urban centres with populations in the millions. Such population expansion and densification increases the strain on wastewater collection and treatment infrastructure, which has been largely based on an end-of-line centralised model. However, in megacities new challenges arise, because provision of suitable sanitation is expensive and it requires infrastructure expansion through construction of extensive sewer networks and larger capacity wastewater treatment plants, which consume more energy. Alternative disposal techniques for solid and liquid waste generated during the treatment process are required, because disposal solutions are decreasing as landfill costs rise and environmental standards are tightened, the latter reducing opportunities for land reuse. Additionally, mass wastewater discharge can have a detrimental impact on the ecology of water bodies and on the health of downstream populations, and requires suitable treatment before disposal. These challenges have the potential to offset the savings that the economies of scale offered by the traditional wastewater collection and treatment systems can impart. The need for affordable and effective wastewater systems in megacities requires the re-evaluation of traditional systems and the re-engineering of water and wastewater transport and resource concepts. Alternative concepts in wastewater collection and treatment, such as decentralised treatment, allied with innovative solutions using current and new technology could play a role in providing affordable and sustainable solutions to deal with the wastewater issue. This paper investigates the scope that integrated wastewater treatment and localised water reuse (in-line treatment, sewer mining), resource recovery (biogas, biosolids), operational changes (timed discharge of sewers, vacuum sewers) and biotreatment (e.g. vermiculture, faecal coliform removal) can play to guarantee the longevity of wastewater infrastructure in megacities. These alternatives offer increased treatment efficiency, recovery of value-added products, and reduce infrastructure cost, whilst maintaining health standards and reducing environmental discharge.G. Tjandraatmadja, S. Burn, M. McLaughlin and T. Biswa

Impediments and constraints in the uptake of water sensitive urban design measures in greenfield and infill developments

Water sensitive urban developments are designed with integrated urban water management concepts and water sensitive urban design measures. The initiatives that may be included are the substitution of imported drinking water with alternative sources using a fit-for-purpose approach and structural and non-structural measures for the source control of stormwater. A water sensitive approach to urban development can help in achieving sustainability objectives by minimising disturbance to ecological and hydrological processes, and also relieve stress on conventional water systems. Water sensitive urban developments remain novel in comparison with conventional approaches, so the understanding and knowledge of the systems in regards to their planning; design; implementation; operation and maintenance; health impacts and environmental impacts is still developing and thus the mainstream uptake of these approaches faces many challenges. A study has been conducted to understand these challenges through a detailed literature review, investigating a large number of local greenfield and infill developments, and conducting extensive consultation with water professionals. This research has identified the social, economic, political, institutional and technological challenges faced in implementing water sensitive urban design in greenfield and infill developments. The research found in particular that there is the need for long-term monitoring studies of water sensitive urban developments. This monitoring is important to validate the performance of novel approaches implemented and improve associated guidelines, standards, and regulatory and governance frameworks, which can lead to mainstream acceptance of water sensitive urban development approaches. The dissemination of this research will help generate awareness among water professionals, water utilities, developers, planners and regulators of the research challenges to be addressed in order to achieve more mainstream acceptance of water sensitive approaches to urban development. This study is based on existing water sensitive urban developments in Australia, however, the methodology adopted in investigating impediments to the uptake of these developments can be applied globally. It is hoped that insights from this study will benefit water professionals in other countries where there is also a move towards water sensitive urban development. © CSIRO 2012

Decentralised systems - Definition and drivers in the current context

This paper explores the current context for decentralised approaches in the provision of urban water services. It examines the recent history of decentralised systems' implementation in Australia and identifies its drivers. The drivers included addressing capacity constraints of centralised systems, mitigating the environmental impact of urban development, and increasing the resilience of urban water systems to episodic droughts and the projected impacts of climate change. The concepts of integrated urban water management and water sensitive urban design were prevalent in many of the innovative approaches used for the provision of decentralised urban water services. However, there remains a degree of confusion among water professionals in the terminology adopted for on-site and decentralised systems. Based on a literature review, consultation with water industry professionals and examination of decentralised urban developments in Australia, this paper has developed a generalised definition of decentralised systems for adoption across the water sector. The definition encompasses the various development scales in which decentralised systems are implemented, and reflects the new functions and characteristics inherent to those systems. © CSIRO 2013

How supply system design can reduce the energy footprint of rainwater supply in urban areas in Australia

In Australia rainwater tanks are used in cities to reduce demand of mains water and increase the resilience of cities to drought. Rainwater is collected in a tank and supplied to a dwelling through a small pump. Typically the energy footprint for rainwater supply (in kWh/kL) is higher than for centralised water supply, but it can also vary markedly from dwelling to dwelling (0.4-11 kWh/kL). This study aimed to understand how the design of the rainwater supply system from the collection tank to the household can reduce the energy consumption of pumping. We examined the operation of a range of system components for rainwater supply, such as pumps, switches and pressure vessels, in a controlled residential environment (a model house) to understand their impact on the energy required for rainwater supply in urban dwellings. Results show that urban rainwater applications have flow and volume requirements which cause pumps to operate at high energy for rainwater delivery. Matching pump sizes to end use requirements and adoption of ancillary devices (pressure vessels and header tanks) have the potential to lower the energy footprint for rainwater supply. However, the energy savings can be constrained by dwelling characteristics, appliances and system design. © IWA Publishing 2013

Rainwater tanks in modern cities: a review of current practices and research

Rainwater tanks often provide a reliable and affordable water supply source in rural and remote areas where piped water supply systems are unfeasible due to economic considerations. However, over recent decades there has been an increase in the adoption of rainwater harvesting as part of the water supply source mix in modern cities. The uptake of rainwater harvesting has been influenced by the rise of ecological sustainable development as a mainstream practice. Rainwater harvesting is now implemented as part of an integrated urban water management approach to alleviate pressure on traditional water supply sources due to increased demand, driven by the rapid growth of urbanised populations. While examples of rainwater harvesting in human settlements can be found since ancient times, there are still gaps in understanding the role that it can play in modern cities. This paper reviews current international experiences with rainwater harvesting, particularly examining the drivers for their adoption in different urban contexts and the impediments faced for greater mainstream adoption. The paper then reviews the current state of research associated with understanding the value of rainwater harvesting in modern cities, which include impacts on reducing mains water demand, public health risks, energy implications, environmental impacts, and cost-effectiveness