An Integrated Framework for Assessment of Hybrid Water Supply Systems

Using soil-moisture drought indices to evaluate key indicators of agricultural drought in semi-arid Mediterranean Southern Africa

Droughts are natural disasters that globally affect large numbers of people each year. While different forms of drought exist, their severity and extent are dependent on critical points of onset. Understanding these onsets is crucial for water, food and energy security, as well as to develop climate change adaptation strategies. This study used the JAMS/J2000 hydrological model to detect agricultural drought using the Soil Moisture Deficit Index (SMDI). The Berg River catchment in Mediterranean South Africa was used as the pilot study area, which experienced a severe drought between 2015 and 2018 and where meteorological drought progressed into agricultural drought that resulted in significant crop reductions and job losses within the agricultural sector. To combat the effects of meteorological shortfalls, water resource management opted to curb agricultural reservoir releases, forcing farmers to rely on groundwater. Modelling results illustrated the importance of detecting headwater stress within the catchment, where in 2015/2017 headwater areas were affected for the first time over the 35-year simulation. Furthermore, regional changes to the groundwater system, during which severe to extremely severe SMDI values (-3 to -4) were simulated, is postulated to be caused by wide-spread groundwater overuse resulting in a 47% reduction in winter (JJA) and a 68% reduction in spring (SON) streamflow. Immediate streamflow reductions were observed, illustrating the low resilience of these systems to meteorological and agricultural droughts, as well as the impacts of water use behavioural changes. By using SMDI in conjunction with a well constrained hydrological model, crucial drought onset triggers can be detected as well as tipping points regarding water use behaviour. As climate change drives an increase in the occurrence of meteorological droughts in many parts of the world, understanding the advance of severe long-term effects is important for the development of effective adaption strategies to promote water, food and energy security.

Comprehensive Assessment of Water Sensitive Urban Design Practices based on Multi-criteria Decision Analysis via a Case Study of the University of Melbourne, Australia

Water sensitive urban design (WSUD), as a typical green stormwater infrastructure (GSI), contains various facilities to decrease the urbanization impacts and enhance the values of amenity, ecosystem, and livability in Australia. Although WSUD has developed over 30 years, existing studies for WSUD performances have sometimes ignored its economic and social benefits, and there is still a lack of an integrated framework to optimize the GSI combinations based on various criteria in a site. This paper aims to utilize “score-rank-select” strategy to comprehensively assess WSUD combination scenarios from functional, economic, social, and environmental aspects, by taking the University of Melbourne (Parkville campus) as a case study. In detail, multi-criteria decision analysis (MCDA) was used for weight determination and scenario comparison. The results showed that scenario 4 with 52% green WSUD facilities had the highest assessment score (0.771) among the five scenarios, while the final score (0.758) of scenario 5 was lower than scenario 4 although its green facility proportion reached 69%. The trade-off relation between the proportion of grey and green WSUD facilities was further demonstrated. Additionally, this paper strongly recommends that the MCDA-based comprehensive assessment framework described here can be generally promoted for the water sector to solve the decision-making problems. The use of such a framework can further promote sustainable development by helping water managers to make informed and inclusive decisions involving a variety of factors.

Human Health, Economic and Environmental Assessment of Onsite Non-Potable Water Reuse Systems for a Large, Mixed-Use Urban Building

Onsite non-potable reuse (NPR) is being increasingly considered as a viable option to address water scarcity and infrastructure challenges, particularly at the building scale. However, there are a range of possible treatment technologies, source water options, and treatment system sizes, each with its unique costs and benefits. While demonstration projects are proving that these systems can be technologically feasible and protective of public health, little guidance exists for identifying systems that balance public health protection with environmental and economic performance. This study uses quantitative microbial risk assessment, life cycle assessment and life cycle cost analysis to characterize the human health, environmental and economic aspects of onsite NPR systems. Treatment trains for both mixed wastewater and source-separated graywater were modeled using a core biological process-an aerobic membrane bioreactor (AeMBR), an anaerobic membrane bioreactor (AnMBR) or recirculating vertical flow wetland (RVFW)-and additional treatment and disinfection unit processes sufficient to meet current health-based NPR guidelines. Results show that the graywater AeMBR system designed to provide 100% of onsite non-potable demand results in the lowest impacts across most environmental and human health metrics considered but costs more than the mixed-wastewater version due to the need for a separate collection system. The use of multiple metrics also allows for identification of weaknesses in systems that lead to burden shifting. For example, although the RVFW process requires less energy than the AeMBR process, the RVFW system is more environmentally impactful and costly when considering the additional unit processes required to protect human health. Similarly, we show that incorporation of thermal recovery units to reduce hot water energy consumption can offset some environmental impacts but result in increases to others, including cumulative energy demand. Results demonstrate the need for additional data on the pathogen treatment performance of NPR systems to inform NPR health guidance.

Urban Multi-Source Water Supply in China: Variation Tendency, Modeling Methods and Challenges

Urban water resources are the basis for the formation and development of cities and the source of urban water supply. However, with the acceleration of urbanization and the explosion of urban populations, the contradiction between water supply and demand in some areas, especially in big cities, has become increasingly prominent. It is simply not sufficient to rely on local conventional water resources to meet urban water demand, and a single source water supply mode has a higher vulnerability, resulting in greater safety risks in urban or regional water supply systems. Therefore, giving full play to the water supply capacity and carrying out multi-source water supplies are necessary and urgent. This paper gives an overview of the optimal allocation of multi-source for urban water supply concerning variation tendency, modeling methods and facing challenges. Based on the variation tendency of water consumption and water supply pattern in China, Tianjin is taken as a typical city for systematically outlining water supply changes and cause analysis. Subsequently, the modeling methods for proposing the optimal allocation scheme are summarized, which are composed of defining the topological relation, constructing the mathematical model and seeking the optimal solution. Ultimately, the current and emerging challenges are discussed including emergency operation of multi-source water supply and joint operation of water quality and quantity. These summaries and prospects provide a valuable reference for giving full play to the multi-source water supply capacity and carrying out relevant research so as to propose the optimal allocation scheme in urban multi-source water supply systems.

Resilient Urban Water Services for the 21th Century Society—Stakeholder Survey in Finland

Resilience has become a vital theme in the discussion concerning urban water services. Resilience in this context can be defined as both keeping up a good level of services, as well as rapid and fluent recovery from failures caused by natural disasters, unsound infrastructure or incorrect management. Although adequate water services resilience can be considered as sustainable, resilience is a wider concept than sustainability. In order to call water services resilient, all sections from policy and management to technical operation should be clear and coherent, and their operation in challenging situations also must be guaranteed. This study seeks a resilient approach to water services through a literature review, and a questionnaire to stakeholders; mainly water supply and sanitation experts. The results show that sufficient technology and good water quality are not sufficient for achieving resilient water services, but also education and institutional management are essential issues. These are accomplished by a methodical education system, capacity building, and good governance.

Managing the Water-Energy Nexus within a Climate Change Context—Lessons from the Experience of Cuenca, Ecuador

The impact of climate change dynamics has a multiplicative effect when the interlinkages between water and energy are considered. This also applies to climate change co-benefits that derive from adaptation and mitigation initiatives implemented at the urban level and that address the water-energy nexus. A better understanding of the water-energy nexus is a precondition for integrated resource planning that optimizes the use of scarce resources. Against this background, the paper assesses the potential impact of water-energy saving technologies (WEST) on the water-energy nexus of Cuenca, Ecuador, focusing on how vulnerability to climate change may affect the water metabolic cycle of the urban area. Water-energy saving technologies such as rainwater harvesting, solar water heaters, and micro water turbines, reduce water-related energy consumption and mitigate greenhouse gases emissions; thereby illustrating the potential to generate climate change mitigation and adaptation co-benefits. The paper relies on primary data collected through interviews and a survey as well as secondary data in order to assess the extent to which water-energy saving technologies influence the water-energy nexus in Cuenca’s urban water metabolic cycle. Within the context of climate change, the paper develops a business-as-usual scenario and assesses how this is modified by the implementation of water-energy saving technologies.

Stakeholder evaluations of risk interventions for non-potable recycled water schemes: A case study

Non-potable recycled water schemes can benefit sustainable urban water management through reducing demand for drinking water and mitigating environmental loadings through the provision of advanced wastewater treatment. However, scheme feasibility can be diminished by high capital and operating costs which can be elevated by perceptions of health risks and subsequently overly cautious risk reduction measures. Conversely, a failure to anticipate the risk management expectations of stakeholders can undermine scheme feasibility through insufficient demand for recycled water. The aim of this study was to explore how stakeholders' perceptions and preferences for risk management and recycled water end-uses might influence scheme design. Using a case study scheme in London, four risk management intervention scenarios and six alternative end uses were evaluated using a stochastic PROMETHEE-based method that incorporated quantitative microbial risk assessment and stakeholder criteria weights together with an attitudinal survey of stakeholders' risk perceptions. Through pair-wise criteria judgements, results showed that stakeholders prioritised health risk reductions which led to the more conservative management intervention of adding water treatment processes being ranked the highest. In contrast, responses to the attitudinal survey indicated that the stakeholders favoured maintaining the case study's existing levels of risk control but with more stakeholder engagement. The findings highlighted potential benefits of understanding risk perceptions associated with different design options and contrasting these with multi-criteria model results. Extrapolating from these findings, future research could explore potential challenges and benefits of providing flexibility in scheme designs to appeal to a wider range of stakeholder needs as well as being more adaptable to future social, environmental or economic challenges. The study concludes that contemporary risk management guidance would benefit from more explicitly outlining constructive ways to engage stakeholders in scheme evaluation.

Shifting Infrastructure Landscapes in a Circular Economy: An Institutional Work Analysis of the Water and Energy Sector

Under pressure by the transition towards a circular economy, the infrastructure landscape is changing. Using Institutional Work as an analytical lens, this article analyses the work actors do to change and adapt institutional structures. In this process of restructuring, the research shows that there are four dominant types of institutional work: Enabling, Constructing Identities, Constructing Normative Networks, and Changing Normative Associations. The increasing fragmentation of infrastructure as well as the increasing connections made between different flows forces organisations to readjust their internal institutions as well as those that guide their interactions with their surroundings such as other organisational actors as well as citizens. Circularity requires a restructuring of infrastructure governance in order to adapt to the increasing flux caused by decentralised technologies and the need for integration of different systems. Additionally, the actors associated with energy and water infrastructure are responding accordingly.

The Potential of Knowing More: A Review of Data-Driven Urban Water Management

The promise of collecting and utilizing large amounts of data has never been greater in the history of urban water management (UWM). This paper reviews several data-driven approaches which play a key role in bringing forward a sea change. It critically investigates whether data-driven UWM offers a promising foundation for addressing current challenges and supporting fundamental changes in UWM. We discuss the examples of better rain-data management, urban pluvial flood-risk management and forecasting, drinking water and sewer network operation and management, integrated design and management, increasing water productivity, wastewater-based epidemiology and on-site water and wastewater treatment. The accumulated evidence from literature points toward a future UWM that offers significant potential benefits thanks to increased collection and utilization of data. The findings show that data-driven UWM allows us to develop and apply novel methods, to optimize the efficiency of the current network-based approach, and to extend functionality of today's systems. However, generic challenges related to data-driven approaches (e.g., data processing, data availability, data quality, data costs) and the specific challenges of data-driven UWM need to be addressed, namely data access and ownership, current engineering practices and the difficulty of assessing the cost benefits of data-driven UWM.