Ferramenta para dimensionamento de reservatório para aproveitamento de água de chuva no Semiárido brasileiro por meio do coeficiente de transbordamento volumétrico

Abstract

Water scarcity in the Brazilian Semi-Arid Region is a historical and structural challenge, exacerbated by climate change and the irregular distribution of rainfall. In this context, Rainwater Harvesting Systems (RHS) emerge as a vital solution for water supply, especially in rural communities. The efficiency of these systems is directly linked to the correct sizing of the reservoir, which is their most costly component. This study proposes the development and application of a tool for sizing rainwater reservoirs in the Brazilian Semi-Arid Region, using the Volumetric Overflow Coefficient (VOC), defined as the ratio between the annual spilled volume and the reservoir capacity. The objective was to create a method that, by minimizing the VOC, would indicate the "optimal" reservoir volume while minimizing losses. The methodology was based on the simulation of the daily water balance for a 30-year historical series (1993-2022), covering the entire semi-arid region. Maps of VOC values generated from 40 scenarios were analyzed, which combined different catchment areas (50 to 200 m²), water demands (domestic and irrigation), and reservoir volumes (2 to 50 m³). The results demonstrated that the catchment area is the predominant factor for system efficiency, with larger areas resulting in higher VOC for the same reservoir volume. It was found that increasing the reservoir capacity beyond 20 m³ generally does not substantially reduce spillage losses. Based on these analyses, a Python algorithm with a graphical interface was developed, allowing the user to input their location, catchment area, and demand to obtain the optimal reservoir volume and the system's reliability. The tool eliminates offers a solid technical basis for planning efficient, sustainable RHS adapted to real local needs.