E. Rozos, and C. Makropoulos, Urban regeneration and optimal water demand management, 14th International Conference on Environmental Science and Technology (CEST2015), Global Network on Environmental Science and Technology, University of the Aegean, Rhodes, Greece, 2015.
Increasing water scarcity has drawn attention to the management of urban water demand, which can be achieved through the re-engineering of the urban water cycle in order to implement water reuse practices. Examples of these new practices include the use of locally treated water for a variety of non-potable uses at household or neighbour scales. However, the successful design and implementation of these new practices is not straightforward. The efficiency of a rainwater harvesting scheme, for example, can be greatly reduced if the local tank is under-dimensioned, whereas the maximum efficiency is achieved with the tank capacity exceeding a threshold, which depends on the statistical profile of both the demand and supply (rainfall). The identification of this threshold requires modelling of the rainwater recycling scheme using long historical timeseries (or synthetically generated with a stochastic model) to capture the statistics of the supply/demand. It should be noted that the tanks per se are relatively cheap, but the space to install them and the preparations required (e.g. excavations in case of underground installation) can have significant costs. Therefore, it is imperative to correctly identify the optimum capacity of a tank. Another costly installation required for a rainwater recycle scheme is the dual reticulation, which, in case of retrofitting, translates into expensive plumbing interventions of which the payback period (if any) is very long. However, dual reticulation can be easily implemented during the construction of a building. Such an opportunity is offered in the region of Eleonas, Athens, Greece. Recently, this area has attracted the attention of many urban planners, who have suggested alternative regeneration scenarios: the Agrarian (the area as a green reservoir for the surrounding city), the Urban-Agrarian (extensive green areas along with residential areas and transportation services) and the Metropolitan (transformation of Eleonas into the new Central Business District for Athens). In this study, these three alternative regeneration scenarios were assessed with UWOT. UWOT is a bottom-up urban water model that simulates the generation, aggregation and routing of demand signals (potable water demand, runoff discharge demand, and wastewater discharge demand). First, UWOT was used to 'scan' the water networks of the three scenarios (assuming conventional water network) to identify the most intense water consumers. Afterwards, a local rainwater harvesting scheme was introduced in the networks of the major water consumers to reduce the water demand on-the-spot. Then, UWOT along with an optimization algorithm were used to properly dimension this rainwater harvesting scheme. The results of the optimization indicated that the runoff volume could be considerably reduced, which will further improve the ecological footprint of the planned regeneration.