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Abstract: Urban growth models developed in the second half of the 20th century have allowed for a better understanding of the dynamics of urban growth. Among these models, cellular automata (CA) have become particularly relevant because of their ability to reproduce complex spatial and temporal dynamics at a global scale using local and simple rules. In the last three decades, many urban CA models that proved useful in the simulation of urban growth in large cities have been implemented. This paper analyzes the ability of some of the main urban CA models to simulate growth in a study area with different characteristics from those in which these models have been commonly applied, such as slow and low urban growth. The comparison of simulation results has allowed us to analyze the strengths and weaknesses of each model and to identify the models that are best suited to the characteristics of the study area. Results suggest that models which simulate several land uses can capture better land use dynamics in the study area but need more objective and reliable calibration methods. [Copyright &y& Elsevier]

Abstract: Many urban areas suffer water scarcity but paradoxically, a local source of water such as rainwater is mostly treated as a risk rather than as a valuable resource. Scepticism regarding the use of rainwater harvesting technologies still prevails today, particularly in low precipitation areas. However, some regions such as the Metropolitan Area of Barcelona (MAB) have started to promote the use of rainwater through specific regulations and incentives. This paper aims to examine the use of rainwater harvesting in the two main types of buildings prevalent in the MAB by analysing users’ practices and perceptions, drinking water savings and economic costs. Despite low precipitation inputs and a high variability of precipitation, daily balances show that toilet flushing demand of a single family house can be practically met with a relatively small tank. Rooftop rainwater can also meet more than 60% of the landscape irrigation demand in both single and multi-family buildings. The main drawback is the long pay-back period that rainwater harvesting systems present today. Nevertheless, it is remarkable that in multi-family buildings residents usually take no notice of the costs associated with the system. In contrast, benefits for the whole society are usually much more appreciated. Users’ reactions and their level of satisfaction towards rainwater harvesting systems suggest that both regulations and subsidies are good strategies to advocate and expand rainwater harvesting technologies in residential areas. However, a multidirectional learning environment needs to be promoted to ensure a proper use of rainwater harvesting systems and risk minimisation. [Copyright &y& Elsevier]