Dynamics and temporal trend of evapotranspiration in semiarid native
forests in Brazil and Spain using remote sensing
Abstract
Evapotranspiration (ET) plays an important role in integrated water
resource planning, development and management. This process is
particularly relevant in semiarid regions. The aim of the present study
is to compare the actual spatial and temporal evapotranspiration (ETa)
patterns and temporal trends in two semiarid forests, one in Brazil
(Aiuaba) and the other in Spain (Valladolid). We used the Surface Energy
Balance Algorithm for Land (SEBAL) to assess the effect of climatic
variation in both areas. In the Brazilian semiarid forest, Caatinga is
the main vegetation, while it is stone pine in Spain. For this purpose,
69 Landsat-5 and 42 Landsat-8 images (1995 – 2019) were used. The
Mann-Kendall test was applied to assess the occurrence of trends in
precipitation, temperature and potential evapotranspiration data; and
the Temporal Stability Index (TSI) to know which areas have greater
seasonal ETa. The annual amplitude of the potential evapotranspiration
(ET0) is the same in both areas, however, the Caatinga values are
higher. In the Caatinga forest, when ET0 presents its highest values
throughout the year, ETa presents the lowest, and vice versa. In the
Pinares forest, ETa follows the ET0 dynamics during the year, and the
difference between ET0 and ETa is maximum during the summer. The
Caatinga forest showed a greater spatial variation of ETa than the
Pinares forest as well as a greater extension with lower temporal
stability of ETa than the Pinares forest. Both the Caatinga forest and
the Pinares forest showed significant annual trends of increase for ET0
and ETa: 3.5 mm and 2.2 mm, and 7.0 mm and 3.9 mm, respectively.