Rainfall and Evapotranspiration Patterns in Goiânia, GO

Abstract

Rainfall (P) and potential evapotranspiration (ETP) are climatic variables relevant to different areas of knowledge, such as: agriculture, watershed management, weather forecasts and urban drainage. The aim of this work was to characterize the rainfall and ETP patterns for the Goiânia, GO city. Data of 36 years for rainfall and 21 years for ETP were used. The precipitation was 1,494.66 mm, with a trend of reduction at a rate of 3.7 mm year^-1. It was observed that 99% of the daily precipitations are p ≤ 50 mm day^-1. We recorded 292 days without rain and 72 rainy days, with a tendency to reduce rainy days and increase dry days. The ETP was 1,380.57 mm, with the highest and the lowest mean recorded in the 3rd (139.02 mm) and 35th (55.36 mm) quinquides. There is a tendency to increase in ETP (6.37 mm year^-1). A water surplus of 607 mm year^-1 and a deficit of 471 mm year^-1 were recorded. ETR/ETP <0.8 between the months of April and October. Predominant frequencies of P and ETP were 38% $\left(P>\overline{X}\right)$ and 31% $\left(ETP>\overline{X}\right)$, with periodicities 4.0 (P) and 3.2 (ETP) years. Correlation of 0.68 between the mean air temperature and Goiás deforestation rates was observed.

Keywords:
water balance; temperature; Brazilian savanna