RECENT TREND OF REFERENCE EVAPOTRANSPIRATION IN THE NORTH-EASTERN REGION OF BANGLADESH

Evapotranspiration (ET), the major component of hydrological cycle, will affect crop water requirement directly. In this research, we investigated temporal trends of reference evapotranspiration (ET0) values in the north-eastern region of Bangladesh. For this purpose, meteorological parameters collected from meteorological site over a 25-years period (1991–2015) 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.