Towards Circular Water Neighborhoods: Simulation-Based Decision Support for Integrated Decentralized Urban Water Systems

Gazing into the Crystal Ball: A Review of Futures Analysis to Promote Environmental Justice in the UK Water Industry

Water is a vital and multifunctional resource for our society, economy and ecosystems; thus, how water is managed now and into the future has wide-reaching consequences. Sustainable water management and environmental justice therefore become key topics; a discussion of these terms is explored in the context of the UK water industry, which provides the focus for this study. This systematic review explores how considerations of the future have been applied in water research. The literature is reviewed with respect to (1) defining the end goal, (2) the use of futures analysis and (3) possible evaluation methods, including a discussion on the boundaries applied to each of the studies. A growing body of research associated with decision-making applying future scenarios was identified. However, the methods of application varied substantially, with holistic analyses largely lacking. The formulation of methods appears to be specific to the goal that is sought as well as the cultural influence of the region in which the analysis was developed and deployed. This paper presents a case for the visualisation of catchment characteristics and interdependencies to enable transparency in decision-making. This should reflect not only the current system but also a range of potential futures to enable appraisal of impacts.

In silico assessment of household level closed water cycles: Towards extreme decentralization

Water management in most of the developed world is currently practiced in a highly centralized manner, leading to major infrastructure and energy costs to transport water. To decrease the impacts of water scarcity and climate change, the decentralization of water can increase local robustness. In extremis, decentralization can involve building or house level water supply and treatment. Here, we constructed a MATLAB/Simulink model for two decentralized water management configurations at the household level, assuming the socio-environmental setting of Flanders, Belgium. Independence from the potable water grid and sewer system was pursued through rainwater harvesting, reuse of wastewater streams fit-for-purpose, and discharge via infiltration. The mass balance for water was calculated over the system boundaries showing high potential for independence from the grid with a reasonable treatment train and storage options. Next, the risk of contaminant accumulation within the circular system was assessed, showing a key limitation on decentralized system performance necessitating a system purge. Up to 59% of system rainwater usage was due to the replacement of this purge. Employing treatment units with high (95%) contaminant rejection efficiencies eliminated contaminant accumulation issues. The raw model output was quantitatively assessed by constructing four newly proposed key performance indicators (KPIs), quantifying system independence, circularity, drought tolerance and local water body recharge, which allowed for facilitated system comparison and communication to stakeholders. A sensitivity analysis was performed in which the effect of input parameter variability and uncertainty on system performance was quantified. The sensitivity analysis showed the importance of water recovery and contaminant removal efficiencies of the applied treatment technologies on system performance when contaminant accumulation in the system forms an issue. In systems not severely affected by pollutant accumulation, parameters such as inhabitant number and roof surface had the largest effect. As a whole, this work shows the potential of extreme decentralization of water systems and addresses the obstacle towards implementation formed by the accumulation of contaminants due to system circularity. Additionally, this study provides a framework for operational and technological decision support of decentralized household-scale water systems and, by extension, for future water policy-making.

Developing a Reliability Index of Low Impact Development for Urban Areas

A defining characteristic of the urbanization is the transformation of existing pervious areas into impervious areas during development. This leads to numerous hydrologic and environmental problems such as an increase in surface runoff due to excess rainfall, flooding, the deterioration of water quality, and an increase in nonpoint source pollution. Several studies propose supplementary measures on environmental change problems in development areas using the low impact development technique. This study investigated the reduction of nonpoint source pollutant loads and flooding in catchments through urban catchment rainfall–runoff management. For the quantitative assessment of flood disasters and water pollution problems, we propose a reliability evaluation technique. This technique refers to a series of analysis methods that determine the disaster prevention performance of the existing systems. As the two factors involve physical quantities of different dimensions, a reliability evaluation technique was developed using the distance measure method. Using the storm water management model, multiple scenarios based on synthetic rainfall in the catchment of the Daerim 2 rainwater pumping station in Seoul, South Korea, were examined. Our results indicate the need for efficient management of natural disaster risks that may occur in urban catchments. Moreover, this study can be used as a primary reference for setting a significant reduction target and facilitating accurate decision making concerning urban drainage system management.

Managing flooding: from a problem to an opportunity

The paper argues that the concept and practice of sustainability have proved too difficult to achieve within traditional water management, and there is a lack of political will to move towards truly sustainable water services. Instead, compromised concepts, including resistance, resilience, ecosystem services, natural capital and adaptation are defining approaches; each of which may contribute partially to sustainability. Pressures due to the changing climate, ecological degradation, human demands, urbanization and deteriorating assets are challenging sustainability and compelling changes to water management. Water is now seen less as a problem to be managed than as an opportunity, as wherever situated, water brings many opportunities to contribute to anthropogenic needs. New ideas are helping to frame the way in which water management is being approached: (i) waste is no longer waste, but a potential resource within a circular economy; (ii) the interconnectedness of infrastructure systems and services and circularity of the water cycle mean there is a need to integrate approaches; (iii) nature-based systems should be preferenced for water infrastructure. These issues and ideas are considered here, together with examples of schemes showing that managing flooding can lead to wider benefits, and potential longer-term sustainability. This article is part of the theme issue 'Urban flood resilience'.