Análise de tendências de variáveis hidroclimáticas na bacia hidrográfica Araguaia-Tocantins e suas implicações na agricultura irrigada

Abstract

The Araguaia-Tocantins Hydrographic Basin (BHAT) is the most extensive in drainage area within the Brazilian territory, with processes of use and occupation increasing in terms of the demands of agribusiness and mineral exploration. In this research, a statistical study was carried out on the hydroclimatic trends (precipitation and flow) in BHAT and its relations with irrigated agriculture. The hydroclimatic mapping based on cluster analysis identified four homogeneous regions within the BHAT, two to the north with a predominance of high rainfall/flow rates and less water availability. In the BHTA the rainy regime occurs between December to March and the dry regime between May and September. The months of October/November (dry to rainy) and April (rainy to dry) are transitional penods with pronounced variations in the seasonal cycle. The geostatistical study of rainfall/river flow forecast revealed that the results using the Box-Jenkings model are relatively better when compared to the Artificial Neural Networks model. The integrated approach of hydroclimatic variables with agricultural data within the BHTA revealed a significant pattern of negative trends in rainfall and flows that are spatially consistent in regions of intense productivity of com and soybeans and cattle. A relevant result was the detection of a significant spatial correlation between the number of central pivots (irrigation) in regions with low water availability, which favor the productivity of temporary crops.