Desenvolvimento de sistema de apoio à decisão para alocação de água na agricultura irrigada em nível de microbacia hidrográfica

Abstract

Family farming is responsible for more than half the world's food production, confirming the need for smart investments in water and irrigation management, through the dissemination of simple techniques for water harvesting, storage, and distribution, as well as through the promotion of new technologies that encourage democratic governance and promote dialogue to achieve an ever more fair distribution of water among users. In this context, this research aims to contribute to the improvement of community self-management of water resources in watershed level, through coordinated and integrated use of irrigation management support tools (e.g., irrigâmetros) and a decision support system for fair water allocation with participation and consensus among users, small farmers, family farm basis. All stages of the implementation of the information system are presented, discussing the methods and results from requirements gathering, integration with irrigâmetros, database building, mathematical modeling of the optimization problem, validation of the capabilities available on the internet and proposition of usage guidelines. As a result, it was developed an optimization routine in order to plan the water distribution over time and space, managing the use of upstream and downstream and avoiding competition at specific times. The process allocates, whenever possible and respecting the flow constraints of watercourses and the useful volumes of the reservoirs, all the available water throughout the planning period, either for irrigation or for reservation, ensuring preference to the priority demands. The modeling of the optimization problem was based on network flow models using linear programming techniques. A database was also provided to store geographical, hydrological and administrative data, as well as all the historical use of water resources, enabling the data management of water availability and demand, and the administrative management of the water rights processes by the management agencies. The user interface is a web application with a distinguished access control that enables specific functionalities to suit each type of user. Besides the basic features of data registration and data query, a simulation module was also provided in the web application, where it is possible to record all the relevant information to run the optimization routine and check the water allocation planning among users, encouraging community participation in decision making. As a demonstration, the system was applied to a hypothetical watershed. In the simulations, ten different crops compete for the available water of a river basin through direct catches over watercourses and reservoirs. In addition to validating the functionalities developed, it was also checked the potential use of the system in assessing the impacts of adjustments in water rights restrictions, inclusions of new crops, changes in working capacity of water harvesting and irrigation systems, adjustments of the available operation period and changes in the design of reservoirs.