WSD is an alternative systems-based approach to conventional urban water management. It encompasses all aspects of integrated urban water cycle management, including water supply, sewerage and stormwater management. The concept represents a significant shift in the way water and related environmental resources and water infrastructure are considered in the planning and design of cities and towns, at all scales and densities (Fletcher et al., 2014).
In South Africa the term Water Sensitive Design is used to allow for a broader focus on the development of not only urban and peri-urban communities, but also those in rural environments. In other parts of the world, the term Water Sensitive Urban Design is used.
WSD emerged in Australia in the 1990s and was expanded on and formalised internationally by the Cooperative Research Centre for Water Sensitive Cities (CRCWSC) in the 2000s. It emerged in response to challenges facing cities including rapidly growing urban populations, changing population dynamics, environmental degradation, climate change and an increasing global focus on sustainability.
From its initial association with stormwater, WSUD has evolved into a broader framework for the holistic management of the urban water cycle – the potable water supply, sewerage system and stormwater drainage system – and its integration into urban design (Wong, 2006). WSUD is linked to the concepts of sustainable urban water management and integrated urban water management, which integrate social, environmental and economic aspects and emphasize resilient, equitable and regenerative approaches.
WSD “...comprises two parts - ‘Water Sensitive’ and ‘Urban Design’. Urban Design is a well-recognised field associated with the planning and architectural design of urban environments, covering issues that have traditionally appeared outside of the water field but nevertheless interact or have implications to environmental effects on land and water. WSUD brings ‘sensitivity to water’ into urban design, i.e. it aims to ensure that water is given due prominence within the urban design processes. The words ‘Water Sensitive’ define a new paradigm in integrated urban water cycle management that integrates the various disciplines of engineering and environmental sciences associated with the provision of water services including the protection of aquatic environments in urban areas. Community values and aspirations of urban places necessarily govern urban design decisions and therefore water management practices. Collectively WSUD integrates the social and physical sciences.” (Wong & Ashley, 2006).
WSD aims to minimise the hydrological impacts of urbanisation on the surrounding environment. The figure below visualizes the natural water balance, the urban water balance - which shows the impacts of urbanisation on the water cycle -, and the WSD water balance. The WSD water balance incorporates elements such as wastewater recycling, managed aquifer recharge, stormwater treatment and harvesting, and waterway naturalisation as means to mitigate the impacts of urbanisation and return to the natural water balance as much as possible.