Modelo analítico de segurança hídrica a partir de Soluções baseadas na Natureza: aplicação na Bacia do rio Guapi-Macacu, RJ

Abstract

The problems related to water scarcity and the degradation of water quality tend to aggravate in the world due to the continuous demographic growth and the increase in water demands; the higher frequency and intensity of extreme hydrologic events (floods and droughts); requiring new management approaches. In this context, “Nature-based Solutions” (NbS), have shown to be a promising way to promote water security, in a complementary way, by increasing the resilience of supply systems in the face of climate change and making the basic human and ecological water needs compatible. The main objective of this study is to propose a conceptual and analytical framework for assessing water security of raw water for public supply based on Nature-based Solutions (NbS), and its application to the Guapi-Macacu river Basin case study. The study adopted the literature review and the case study as research strategies, and differente methods were used: bibliographic research, document analysis, interviews and participant observation. The application of the analytical model identified the high level of water availability compromise in the Guapi-Macacu river Basin, the frequent scarcity of water in times of drought, and the emergence and aggravation of conflicts over water use, requiring urgent management actions. It was found that the basin has biophysical, social and economic characteristics that are mostly favorable for the implementation of NbS. The NbS proved to be relevant for increasing water security, potentially contributing to reducing the risk to the stressors "Land use and cover", "Erosive processes", "Polluting load" and "Interference in water bodies". The analysis of NbS-related initiatives demonstrated the involvement of many actors and different sectoral policies, which, however, lack an integrated vision and understanding for water security and the set of actions. With the exception of conservation actions, the results of NbS initiatives are still limited, and it is necessary to expand ecological restoration interventions and good agricultural practices at scale in the basin. The absence of monitoring actions for ecosystem services related to water security made it impossible to estimate the magnitude of the impacts of NbS. Among the recommendations for improvement, we highlight: strengthen capacities for the formulation, selection, conception and implantation of NbS; promote greater intersectoral and institutional cooperation; leverage continuous and long-term financing mechanisms; promote NbS cost reduction; raise awareness of society and decision makers; and fill gaps and promote methodological advances for quantifying and valuing the costs and benefits of NbS.