Modelagem da fragilidade ambiental da bacia de contribuição do Açude Gavião, Ceará, Brasil

Abstract

The expansion of human activities through the exploitation of natural resources has caused changes that weaken environmental systems. River basins are part of this context. These environments have undergone intense anthropogenic transformations that have led to imbalances in their river dynamics, generating social and economic impacts, especially in relation to artificial reservoir basins intended for public supply. Integrated approaches, from a systemic landscape perspective, such as the study of environmental fragility, are one of the proposed ways to reconcile human activities with the carrying capacity of environmental systems. Therefore, this study aims to analyze the environmental fragility of the Gavião reservoir's contribution basin, based on the integration of physical components (geomorphology, pedology, vegetation, and rainfall intensity) with current land use and occupation. To this end, the methodology of Ross (1994; 2012) was adopted, with adaptations by Crepani et al. (2001) and Costa, Oliveira, and Santos (2020). For the integration of data in a GIS environment, map algebra was applied using the arithmetic operation of addition, without assigning differential weights between themes. In this sense, three levels of potential fragility were obtained: medium (corresponding to 80.6% of the study area), strong (17.6%), and very strong (1.7%). Due to anthropic insertion, the emerging fragility highlighted some environments that underwent changes in the degree of fragility. The areas of medium fragility went from 80.6% to 57.4%, that is, a decrease of 23.2 percentage points, with this difference being transferred to the strong and very strong classes. The strong fragility classes totaled 39.9%, a jump of approximately 22.3 percentage points. The very strong fragility areas reached 2.7%, an increase of 0.9 percentage points. In addition, a direct relationship was noted between land use and occupation and the increase in the degradation of river environments. The study of environmental fragility proved to be an essential tool that integrates the natural environment and anthropic actions, facilitating the identification of priority areas for the implementation of public policies aimed at territorial planning and management.