Aproveitamento racional de açudes não estratégicos para irrigação de culturas agrícolas temporárias no semiárido brasileiro

Abstract

In semi-arid regions such as the Brazilian Northeast, the intermittent hydrological network, irregular rainfall, frequent droughts and high evaporation rates leave the population vulnerable in relation to water supply. Despite this, the region has a dense network of reservoirs built by the government and civil society. The large reservoirs monitored by the public authorities are said to be strategic, being intended to supply large urban centers, industrial and agricultural projects, etc., while the non-strategic reservoirs, not monitored by the public authorities, and of great importance in serving rural communities, for human and animal supply and smaller irrigated agricultural production. In order to enable rational water management in non-strategic reservoirs for irrigation in dry regions, the physical/mathematical model NeStRes, was developed, which evaluates the trade-off between evaporation and water withdrawal for irrigation and calculates the maximum yield of irrigated crops. Given the above, the objective of this work was to define conditions for irrigation of temporary crops from non-strategic reservoirs in the Brazilian semi-arid region, with a view to maximizing the irrigator's income. Therefore, the model was applied to five short-cycle crops, namely: rice, sweet potatoes, beans, corn and sorghum in twenty-three dams belonging to the Fogareiro catchment in the state of Ceará. Due to the fact that the model is composed of three modules (hydrological, agricultural and economic) the variables of reliability of water supply, withdrawal, irrigable area and relative income were evaluated. The data showed that the use of water from non-strategic dams for crop irrigation had a maximum yield when the dams were operated in average with the water being used in one third of the time, that is, using water from non-strategic dams in a rational way for temporary agricultural irrigation in the semi-arid region, there are lower evaporation losses and higher financial returns.