This study aimed to identify spatial and temporal variability as well as trends in rainfall
in the state of Tocantins through geostatistical techniques; estimate the water availability for
the state of Tocantins, through pluviometric and fluviometric stations, for spatial distribution
of surface water availability through specific yield; determine the water poverty index of
Tocantins municipalities and analyze the pressure exerted by agribusiness on the state's water
resources. Mann–Kendall trend tests were carried out to evaluate the collected rainfall
information, and later the geostatistical analysis was carried out based on the adjustment of the
theoretical semivariogram model, from the obtainment of values for the structural parameters
such as the nugget effect, the contribution and the range, considering the spherical, exponential
and Gaussian models, applying the weighted least squares adjustment method. For the
regionalization of flows, the index-flood method was adopted, in the sequence: I. Regional
Analysis of Data Consistency; II. Organization and dimensionless series; III. Definition of
empirical frequency curves for each hydrometeorological station; IV. Definition of
homogeneous regions and regional frequency curves. To determine the water poverty index,
the script followed was the classification of municipalities by precipitation range in the dry and
rainy season; determination of the municipality's water production, considering the basin in
which it is inserted, in the dry and rainy season; adequacy of the environmental component
classes, based on the percentage of native vegetation cover; normalization of data due to the
diverse nature to which each one belongs and assignment of weights to the values obtained
from each component of the water poverty index. In the last stage, a survey of information and
references related to Tocantins agribusiness was carried out with the objective of presenting the
evolution of agricultural activities in the State of Tocantins, highlighting the expansion of the
main agricultural crops and cattle raising, in dialogue with the results on the temporal and
spatial distribution of rainfall, the regionalization of flows and the HPI (Water Poverty Index)
in the state territory. Information related to agribusiness in Tocantins was obtained through a
survey with the GeoPortal of the Secretariat for Planning and Budget of the State of Tocantins,
IBGE, in addition to a bibliographical survey that deals specifically with agribusiness in that
state. In the distribution of rainfall, the exponential model presented the best performance in
most of the analyzed situations, verifying the suitability of the geostatistical techniques in the
interpolation of the monthly precipitation for the state of Tocantins. As for the flows, the trend
analysis for defining the feeling of the homogeneous regions of the dimensionless flows was
considered efficient for the sub-basins comprised by the territory of Tocantins. The adjusted
regional functions were suitable for use respecting the application limits (drainage areas) and
observing the caveats regarding the behavior of the curves. Most of the municipalities in
Tocantins presented a water poverty index classified as good, a fact observed considering the
average of the municipalities to determine this indicator for Tocantins, which cannot be
interpreted as an abundance of water resources. The great variation of information related to
agribusiness in the 139 municipalities of Tocantins is evident, which also follows the disparities
presented in the distribution of rainfall, with the lowest annual values in the southeast portion;
the regionalization of flows, which reveals greater concern with the southern region; and with
the IPH, which has a higher concentration of municipalities in a critical situation in the north
of Tocantins. The results therefore indicate priority situations, where greater pressure from
agribusiness on the use of water and greater vulnerabilities related to water resources converge.
Adding up the area destined for agribusiness, considering rice, sugar cane, corn, soy and cattle
raising, 24 municipalities had a value greater than 100 thousand ha. In this relation, in Porto
Nacional this indicator is classified as “very good|”, Dois Irmãos and Bandeirantes do Tocantins
present this indicator classified as “poor”. Based on this combined area, Araguaçu, Peixe and Formoso do Araguaia are the ones with the greatest extension, over 200,000 ha. These
municipalities fit the classification of this indicator as “good”.
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