Avaliação dos recursos hídricos da sub-bacia do Ribeirão Baguaçu visando diagnóstico e soluções ambientais sustentáveis

Abstract

The headwaters of the Baguaçu Stream are located in the municipality of Coroados, in the northwestern region of the State of São Paulo, Brazil. Along its course to the confluence with the Tietê River, the stream passes through the municipalities of Bilac, Birigui, and Araçatuba, providing raw water for multiple uses and purposes. Changes in land use and occupation, together with variations in the seasonality and spatial distribution of rainfall, have resulted in successive periods of water scarcity within the sub-basin. Institutions responsible for water management and supply have expressed growing concern regarding the risk of public water shortages. Within the study area, this research aimed to: (a) characterize the socioeconomic and environmental aspects of the sub-basin, including climate, soils, topography, land use and occupation, sanitation, population distribution, and economic activities, as well as its physiographic features (physical and morphometric characteristics), surface water availability and quality (mean and minimum flows), and water demand, with emphasis on surface water demand; (b) diagnose the main problems, providing technical support for integrated and sustainable management of local water resources; and (c) propose potential solutions. The results showed that only 4.62% of the sub-basin’s area retains native vegetation. Current patterns of land use and occupation, combined with the physical and physiographic features, have contributed to erosion and the silting of watercourses. Between 2010 and 2024, the annual average rainfall decreased by 6.44%, and between 2020 and 2024, by 8.41%, compared with the historical average from 1970 to 2024. These reductions led to a decline in water availability (Q7-10) of 10.12% from 2010 to 2024 and 13.35% from 2020 to 2024. The largest granted water demand in the sub-basin corresponds to surface water abstraction. Although most water use permits were issued for irrigation, the main consumers of surface water are public supply systems, followed by industrial activities. The analysis of water demand and availability data revealed a deficit in the study section, indicating a potential risk to water security, particularly during periods of greater scarcity. This study thus identified not only the risks associated with water resources management but also the significant potential and the essential need for collective efforts to protect water—a finite natural resource and a public good belonging to all Brazilian society. In this context, the strategic role of regulation is emphasized as a State instrument and an expression of UNIVERSIDADE BRASIL www.ub.edu.br the public interest, endowed with legal authority and appropriate mechanisms to guide and influence the behavior of service providers. Such instruments can promote the integration between economic development and the objectives of water security, environmental preservation, and the conservation of water sources.