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Giving some specific precipitation regimes and technical design parameters, urban Rainwater Harvesting Systems (RWHS) may represent an alternative source to drinking water supply system promoting its conservation and rational use. The use of RWHS requires the definition of generic and simplified method for sizing RWHS accumulation tanks, which is has being considered the most expensive component of the system. Additionally, several methods have being used to define reservoir volumes leading to a wide variety of final reservoir volumes many of them over estimated. The main objective of this article is to present a new methodology to define RWHS reservoir volumes considering technical and economic viabilities of the systems. The proposed methodology was incorporated into a Decision Support System (DSS), named SARA. The method provides an alternative way to define smaller RWHS reservoir volumes once it accepts lower levels of reliabilities giving that the RWHS is considered a complimentary system, better suited for urban areas. RWHS design diagrams are built as a result of the methodology in an attempt to offer a tool to initial and rapid design of reservoir volumes for RWSH. The method was applied to different urban areas in Brazil.

The increase in runoff volume due to urban sprawl has imposed a challenge to current urban drainage systems and future projects in order to add sustainable strategies for effective flood control especially in consolidated urban areas that would require retrofitting of urban areas with additional social and economic costs. This study is aimed at evaluating alternatives of drainage solutions in a consolidated urban area in the Federal District of Brazil, located in Savanna region, based on the reduction of peak flow and flooded volume in the areas exposed to flood hazard. Different solutions based on the concepts of Low Impact Development (LID) were simulated, showing that the current traditional drainage system is not in compliance with local regulations in the Federal District. In addition, the use of permeable pavements and stormwater ponds could reduce at least 46% of the flooded volume. When placed along with the drainage network, not only at the outlet, stormwater ponds were able to reduce the flooded volume and its hazard and damages. However, LIDs solutions were not able to completely eliminate floods in the region. Structural changes, as resizing the conduits into the drainage systems in the area, could improve the drainage system effectiveness avoiding floods and respective hazards and damages.

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ABSTRACT The environmental systems associated with water resources management have always been represented through physical factors and processes. In order to consider the social system coupled with the environmental system, a new modeling approach emerges, the agent-based modeling. Two steps are essential to build agent-based models-ABMs. The first step requires the agent behavior understanding and considers the influence of external factors in the agent decision-making. The second one is the system representation through an ABM. In this perspective, the WaDiGa water management role-playing game-RPG was applied to map the rural producers' behavior of a peri-urban region. In addition, an ABM was developed in the GAMA platform intended to represent the agents’ behavior and its consequences in the environment configuration. After applying the proposed methodology, it was concluded that the WaDiGa was able to identify factors that influence the local agents' decision-making, and that the game fulfills the function of a dialogue platform on the water resource theme, and could be used as a tool for environmental education and socio-hydrological modeling. The ABM developed was able to represent the relationship between the agricultural production of the community and the water use, presenting results similar to the results obtained in the WaDiGa.