Compound effect of land use and land cover and ENSO on the discharge of subbasins in the Amazon.

Abstract

Evaluate the compound effect of land use and cover and ENSO (El Niño-Southern Oscillation) on the streamflows of two paired subbasins of the Itacaiúnas River Basin (IRB), Brazilian Eastern Amazon. Specific discharge data were determined using rating curves for the period from 01/27/2020 to 01/27/2022. ERA5-Land reanalysis data were used to assess mean precipitation and land use and land cover maps were used to assess changes in land cover dynamics. The region was influenced by La Niña of weak intensity that lasted 3 years. In 2020, during the rainy season, the sign of land cover prevailed in subbasins hydrographs variability. Thus, the main flow rates of the pasture were higher than those of the forest. And during the dry season, the mean flow rates of the forest were the highest. However, in 2021, the La Niña signal became moderate in intensity, modifying the hydrographs. The two subbasins did not undergo significant changes in land use and cover from 2020-2021 and were subjected to the same climatic conditions. Therefore, the increase in minimum discharge in the pasture subbasin in 2021 was a consequence of the moderate La Niña event in the Niño region 3.4.