Hydrological Models as a Tool for Sustainable Use in the Conservation of Water Resources in the Northeast Region of Brazil

Introduction: Mathematical models for environmental predictions have become a very common technique among researchers and water resources managers. Furthermore, they play a crucial role in decision support systems and in the planning of these resources, as they are capable of simulating different development scenarios, thus supporting sustainable management. The combination of environmental monitoring with mathematical modeling provides a more advantageous cost-benefit ratio compared to exclusively local monitoring. These models can simulate environments with specific types, although few are capable of integrating the simulation of water quality and quantity on a scale that covers the entire river basin. Seven models widely used around the world are: AQUATOX, CE-QUAL-W2, EFDC, QUALs, SWAT, SPARROW and WASP. These models were developed for specific conditions in certain regions, with the United States, China and South Korea being the countries that use them most. The SWAT model is the most frequently used, followed by the QUAL and CE-QUAL-W2 group models. Objective: The objective of this study is to present a review of hydrological water quality models, identifying the main models used, their uses and applications in Brazil and the Northeast over the last 10 years. Theoretical Framework: The use of water quality models is quite versatile and can be adjusted to different study objectives and types of environments. The integration of environmental monitoring with mathematical modeling provides a greater economic benefit in relation to monitoring restricted to local areas, as it takes into account the spatial and temporal distribution of the data obtained, the impacts of human activities and the specific demands of the river basin . These models are also applied to solve issues related to planning and quantitative management of water resources, acting as a Decision Support System. Method: The methodology adopted for this research comprises a literature review of a total of 295 documents extracted from the Web Of Science (WOS) and Scopus databases, considering the period from January/2013 to May/2024. Publications in English and Portuguese language scientific journals were selected, with peer review. Results and Discussion: The study observed 11 widely used models, of which six present articles published with studies in the Northeast region of Brazil, totaling 42 scientific publications in the period surveyed. The SWAT model (Soil and Water Assessment Tool) is widely used among researchers from different regions of the country, in the Brazilian northeast it was the most observed model in scientific works, with 18 publications, and in Brazil it totaled 142 works. Among the northeastern states, Ceará presents the largest number of published works with 14 articles. Research Implications: In the Northeast region, models for water quality are still a little explored tool, with the use of models for climate change and predictions of extreme events being more frequent. The application of hydrological models as a tool for optimizing water resources can promote an increase in data available for planning and water management in the semiarid northeastern region. Originality/Value: This study offers an important contribution to the literature by presenting an overview of the main approaches and models aimed at planning and managing water resources. To date, there are no publications that carry out a comprehensive survey of the models and strategies applied in the Northeast region of Brazil, considering the major challenges related to water security. The use of hydrological models as a tool for optimizing water resources can increase data availability, facilitating planning and management in the semi-arid northeast.