GESTÃO HÍDRICA E QUALIDADE DA ÁGUA NO SEMIÁRIDO BRASILEIRO: UMA ANÁLISE DO ÍNDICE DE QUALIDADE (IQA) E DO ESTADO TRÓFICO (IET) NO AÇUDE SANTA CRUZ DO APODI, RN

Abstract

Water resource management in semi-arid regions faces critical challenges due to natural scarcity and anthropogenic pressures. This study analyzes water management and quality at the Santa Cruz do Apodi Reservoir (ASCA), the third-largest reservoir in Rio Grande do Norte, located in the Apodi-Mossoró River Basin (BHRAM). The methodology involved monitoring six strategic points between September 2024 and July 2025, using the Water Quality Index (WQI) and the Trophic State Index (TSI), in addition to collecting water abstraction permit data from the Rio Grande do Norte Water Resources Management Institute (IGARN). The results indicated an allocated abstraction volume of 61.92 hm³/year, intended primarily for river perennialization and human supply. The WQI was classified as "Excellent" (averages between 81 and 84), demonstrating high seasonal resilience. However, the TSI revealed episodes of eutrophication (mesotrophic state) at specific points, influenced by fish farming, agricultural and livestock activities, and tourism. It is concluded that, although the current water quality is satisfactory, the sustainability of the water source depends on strengthening management instruments, such as enforcement and water use charges, which are essential to mitigate the risks of environmental degradation in the face of growing multi-sectoral demand.