A influência do uso do solo na calibração do modelo SWAT para a Bacia do Rio das Almas - Goiás

Abstract

The objective of this monography was to analyze the influence of changes of the soil use and its accupation on the calibration of a hydrosedimentological model for the Almas river basin, located in the cerrado biome, State of Goiás, Brazil. In this study, the Soil and Water Assessment Tool (SWAT) model was used integrated to the Geographic Information System ArcGIS, using in its processing climatological data, use maps and soil occupation, soil types and the digital elevation model. SWAT was applied to three land use scenarios (scenario 1 = 1991, scenario 2 = 2017 and scenario 3 = 2006) and using the same climatic conditions, the first two for calibration and scenario 3 for simulation with the best parameterization obtained with the best fit between observed and simulated flow rates. Simulated flow rates were compared with the observed flow rates from the Colônia dos Americanoos and Jaraguá stations, from 1974 to 1980 (calibration) and from 1981 to 1988 (validation). The performance analysis of the model was measured from the Nash-Sutcliffe index (NS) and the Pearson determination coefficient (R²). To a better model adjustment, the calibration process was performed through the SWAT-CUP program for the colônia dos Americanos, where 11 parameters were calibrated in the basin, which were considered more influential in the hydrological process. The results of the calibration were: (a) scenario 1: R² = 0.88 and NS = 0.74 and (b) scenario 2: R² = 0.84 and NS = 0.70. The results of the calibrations can be considered satisfactory. For the validation process the results obtained were: (a) scenario 1: R² = 0.80 and NS = 0.56 and (b) scenario 2 R² = 0.87 and NS = -0.18. Regarding the validation, it can be observed that in scenario 2 the calibration performed was not representative for the validation period. Scenario 1 presented the best parameterization to represent the basin and to verify its representativeness under different soil uses, the parameterization was applied to scenario 3, obtaining R² = 0.88 and NS = 0.76. The estimated sediments production ranged from 11.7 to 129 ton / ha / year for scenario 1 and for scenario 2 ranging from 64.94 to 348.61 tons / ha / year. The relation between the data of flow rate, observed for the Colônia dos Americanos, and the calculated sediments production presented R ² = 0,79 and R ² = 0,90 for the sceneries 1 and 2, respectively. The soil loss was higher for the sub-basins with predominance of agriculture, cambisols and declivity varying from 1 to 10%. The results show that the model has a good representativeness for the study area and its different uses of the soil.