Modeling the effects of urban growth scenarios on water demand and runoff patterns in Dublin, Ireland

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The concept of sustainable urban water management involves managing the urban water cycle in a holistic manner by integrating the water supply, wastewater and stormwater management of a city to achieve better assimilation of the urban and natural water cycles. In response to the emergence to this new paradigm, decision support models have been developed to facilitate integrated modeling of the urban water cycle and to provide functionality for comparing options for alternative water management options. Outputs typically include indicators such as whole life costs, water flow indicators and energy use. Available models however have shortcomings and tend to have limited capacity to incorporate urban land use changes and the significant but related effects that different urbanization scenarios will have on the urban water cycle. Against this background, the Dynamic Urban Water Simulation Model (DUWSiM) has been developed. DUWSiM is a computer based model that links a cellular automata land use dynamics model (MOLAND) with concepts from existing water balance models. DUWSiM simulates major components of the urban water cycle including, evaporation, runoff, water demand, water supply and wastewater on a daily time step and incorporates urban land use change scenarios on an annual basis for 20 years into the future. DUWSiM has been applied to the Greater Dublin Water Supply area in Ireland to assess the effects of four urban development scenarios based on regional planning policies on water demand and stormwater runoff from 2007 - 2026. It was shown that significant differences in water demand and stormwater runoff exist between urban planning scenarios and it was concluded that urban planners and urban water managers need to collaborate in order to develop effective long-term strategies for the urban water sector. The scenarios assessed were all based on the same population and economic projections and all assumed low and medium density development of urban fabric. Future research should assess the combined effects of regional planning policies, population and economic projections, climate change and urban form (low density vs. high density/compact development) on the urban water cycle.