Integrated urban water management (IUWM) is a philosophy of varying definitions and interpretations. According to the authors of the book entitled, "Integrated Urban Water Management: Humid Tropics", IUWM is described as the practice of managing freshwater, wastewater, and storm water as components of a basin-wide management plan. It builds on existing water supply and sanitation considerations within an urban settlement by incorporating urban water management within the scope of the entire river basin.[1] One of the early champions of IUWM, SWITCH is a research program funded by the European Union and seeks to shift urban water management away from ad hoc solutions to a more integrated approach.
IUWM is commonly seen as a strategy for achieving the goals of Water Sensitive Urban Design. IUWM seeks to change the impact of urban development on the natural water cycle, based on the premise that by managing the urban water cycle as a whole; a more efficient use of resources can be achieved providing not only economic benefits but also improved social and environmental outcomes. One approach is to establish an inner, urban, water cycle loop through the implementation of reuse strategies. Developing this urban water cycle loop requires an understanding both of the natural, pre-development, water balance and the post-development water balance. Accounting for flows in the pre- and post-development systems is an important step toward limiting urban impacts on the natural water cycle.[2]
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Activities under the IUWM include the following:[3]
According to Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO), IUWM requires the management of the urban water cycle in coordination with the hydrological water cycle which are significantly altered by urban landscapes and its correlation to increasing demand. Under natural conditions the water inputs at any point in the system are precipitation and overland flows; while the outputs are via surface flows, evapo-transpiration and groundwater recharge. The large volumes of piped water introduced with the change to an urban setting and the introduction of vast impervious areas strongly impact the water balance, increasing in-flows and dramatically altering the out-flow components.[2]
One of the most significant challenges for IUWM could be securing a consensus on the definition of IUWM and the implementation of stated objectives at operational stages of projects. In the developing world there is still a significant fraction of the population that has no access to proper water supply and sanitation. At the same time, population growth, urbanization and industrialization continue to cause pollution and depletion of water sources. In the developed world, pollution of water sources is threatening the sustainability of urban water systems. Climate change is likely to affect all urban centers, either with increasingly heavy storms or with prolonged droughts, or perhaps both. To address the challenges facing IUWM it is crucial to develop good approaches, so that policy development and planning are directed towards addressing these global change pressures, and to achieving truly sustainable urban water systems.[4]
Instituto Cinara from Universidad del Valle in Cali, Colombia has been jointly working with its local, national, and international partners to contribute on different projects in the hopes of achieving a paradigm change in water management when applied to urban environments. CINARA projects are based on a holistic vision whereby water is managed as a limited and multi-use resource, solutions are proposed under adequate allocation and protection criteria, and the water basin is considered as a planning unit. Furthermore, the CINARA approach demands inter-sectoral and multidisciplinary work and finally, all innovations should include tools and strategies that facilitate the integration of different technical, social, and economical disciplines in regards to water resource planning.[5]
Assessing the effectiveness of IUWM strategies can be a difficult task, particularly for complex systems, or when considering a wide range of IUWM options. Predictive modelling provides a powerful and accessible way to assess different IUWM strategies.
Urban Developer is an integrated urban water management (IUWM) modelling tool developed by the eWater CRC, that has been designed to meet the needs of water professionals facing the challenges of integrated water cycle service planning, management and assessment activities. Urban Developer provides the ability to simulate all three urban water cycle service networks (water supply, stormwater, wastewater), at scales ranging from the sub allotment through to large clusters, or small subdivisions.
Urban Developer can be used to support a range of planning, management and design activities in the urban water sector. In particular Urban Developer has been designed to represent multiple water cycle service systems and/or their interactions. It can be equally applied to greenfield or redevelopment projects and can be used to assess the benefits of retrofitting existing developments. The following, are some examples of the types of modelling exercises Urban Developer is designed to support:
An example of IUWM is the Catskill/ Delaware water system that provides 1.4 billion US gallons (5,300,000 m3) of water per day, including to all of New York City. The IUWM process included an extensive stakeholder engagement process, whereby the needs of all parties were included into the final management plan. A partnership was created between New York City, the agricultural community, and the federal government. The case has become a model for successful IUWM.[6]