Recent Trend of Reference Evapotranspiration under Climate Change Perspective: A Case Study in the North-Eastern Region of Bangladesh

Many processes in the earth surface are affected by climate change. Climate change affects
environment, evapotranspiration (or crop water demand), and water resources. Evapotranspiration
(ET), the major component of hydrological cycle, affects crop water requirement directly. The
objective of this study was to investigate the temporal trends of ET0 in Mymensingh region, the northeastern
part of Bangladesh. For this purpose, meteorological parameters collected from
meteorological site over a 25-year period were used. Two statistical tests including Mann-Kendall and
Sen’s slope estimator (using MEKESENS software) and linear regression (t-test for significance of
slope) were used for the analysis. The same analysis was also performed on governing
meteorological variables to identify the cause of existence of such trend in ET0. The results showed
decreasing trend of ET0 in dry season (Oct. – March), which is mainly caused by decreasing mean
temperature and consistent decrease in wind speed. In wet season (April to September), increasing
trend was observed in July only; while the other months except September showed decreasing trend.
From the results of the two tests (i.e. MAKESENS Software and Linear Regression), it is revealed that
these tests had almost similar performance in detecting trend.