Editorial

Abstract

Achieving sustainable clean water for all and managing urban flood risk are two grand challenges for our societies. Both of them are strongly linked to climate change, urbanisation and ageing of infrastructures. Addressing them requires new paradigms to be developed through novel multi-and interdisciplinary approaches involving engineering and other disciplines, such as governance. The interplay between these two grand challenges is remarkably demonstrated by the first two contributions in this issue. In a briefing article, Caffoor et al. (2017) report on an on-going initiative aimed at delivering disruptive socio-technical solutions for water service provision; whereas the paper of Mugume et al. (2017) investigates the influence of rainwater harvesting on the resilience of urban drainage systems to flooding. Caffoor et al. (2017) reflect on the sustainability of current water supply systems, which rely heavily on centralised, ageing and rapidly deteriorating buried infrastructure. While innovative sensing techniques using autonomous vehicles could be game-changing to achieve cost-effective asset rehabilitation, alternate options include the development of water treatment at the point of use and the use of distributed sources from green infrastructure such as sustainable urban drainage. Particularly, rainwater harvesting has the potential to deliver multiple benefits in terms of water supply, water quality compliance and storm water control, as also exposed by Mugume et al. (2017).Caffoor et al. (2017) go one step further by highlighting the natural linkage between water and energy infrastructure, viewing the former as an opportunity for distributed energy storage, heat transfer and recovery, as well as distributed generation of renewable energy. These issues relate closely to an overarching objective of sustainable cities, which consists of moving from an open system depending on the hinterland (e.g. for providing water and energy) towards a more circular model (EEA, 2015). As engineering cannot solve these challenges alone, socio-technical solutions are necessary to reach truly adaptable and resilient water systems.The concept of resilience plays a key part in the analysis detailed by Mugume et al. (2017). Resilience-based approaches assess the continuity and efficiency of system functioning during or after the occurrence of a system failure. Mugume et al. (2017) apply the so-called global resilience analysis method to evaluate the performance of the wide-scale implementation of dual-purpose rainwater harvesting for a case study in Kampala, Uganda. A broad range of failure scenarios is tested, involving random cumulative failures in the links in the urban drainage network. For each scenario, the residual functionality of the system is quantified. In the considered case study, the catchment-scale implementation of multifunctional systems proves more effective than conventional single-objective approaches for reducing impacts of urban flooding. The most promising results are obtained for strategies combining rai...