With a growing global population and a rising global temperature, there is likely to be reduced water availability.  Peoples’ needs and demands for water use are multifaceted and there is an increase of water-related environmental problems.  Urban areas around the world face the challenge of supplying their residents with clean, sanitised water, but without leaving an impact of the natural environment.  There is demand for innovative sustainable water infrastructures that will make cities ‘greener’, which include economic, social and environmental factors that interact with one another.  Four historical paradigms of urban water management can be identified, and there is now an emerging fifth paradigm.  It is this paradigm that will pave the way for future cities, enabling them to manage urban water in ecological, economical and efficient manner.  In the case of urban water systems, in order to be sustainable, they need to meet the demands of not only humans, but of the ecosystems within the environment that is surrounding them for the present, but also the future.  They need to be able to support this at local and global levels.  Water needs to be used in sufficient quantities and quality, and to protect humans from damages brought on my natural and human disasters that will affect sustaining life.

Using various examples of new sustainable water systems across the world including; BedZED in the United Kingdom; the Pimpama Coomera scheme in Australia; and the Las Vegas valley in the United States of America, a critical review was made to determine if there were any recurring factors that were relative to the success rate of the case study.  To evaluate the case studies, a systems thinking approach was used so to obtain a holistic viewpoint when assessing the sustainable urban water systems.  The sense of hierarchy of urban water systems was described showing that there are many different levels of systems that have different functions and relationships with urban water systems.  In order to achieve sustainable urban water systems that can be used for future generations, a holistic view is imperative so that it is not just the innovative water systems that form part of the system, but other social, economic and political systems.  The below table gives a summary of findings from the case study and literary review from using a systems thinking approach.  By looking at each component separately, barriers are easy to foresee.  Once these are know, mitigating pathways can be drawn up from previous experience.  As always, each stakeholder will have a different view on the sustainable urban water system, which makes it even more important to use a holistic approach. 

It was determined that using a systems thinking approach is necessary when planning and assessing urban water systems as their success rate often relies heavily on the system users, which is the general public.  Using a systems thinking approach, barriers within urban water systems were identified, along with what can be done to mitigate these barriers.  For each case study the system boundary was identified, along with the system components and also the system environment.  Each component and system interact with one another to produce the urban water system, so by identifying all relationships and the needs of an urban water system, lessons can be learnt for future projects.