Climate-induced historical drift of reference evapotranspiration in Mymensingh region of Bangladesh

Climate change impact on evapotranspiration

Abstract

Reference crop evapotranspiration (ET_o) is essential for planning and management of irrigation to ensure optimum utilization of a region’s available water resources. ET_o being an indicator of atmospheric evaporative demand provides a measure of the integrated effect of climatic parameters like solar radiation, wind, temperature and humidity. Variation of these climatic parameters over long period of time alters ET_o. The modified ET_o is crucial for periodic adjustment of irrigation planning and management. This study evaluated variation of ET_o and contribution of the climatic parameters to ET_o-variation in Mymensingh region of Bangladesh by analyzing climatic data of 28 years (1990–2017). ET_o was determined by FAO Penman-Monteith method and trends of ET_o and its governing climatic parameters were evaluated by MAKESENS trend model. The ET_o-governing climatic parameters revealed contrasting trends, which also varied in different months of the year. Net radiation and wind speed showed decreasing trend, while temperature and saturation vapor pressure deficit showed increasing trend. In spite of contrasting contributions of the climatic parameters, their combined effect reduced ET_o with a resulting decreasing trend of the monthly average daily ET_o over the months of the year except July. These results enhance our understanding of the effects of climate change on ET_o and can help correct-planning of water resources for irrigated agriculture.

J. Bangladesh Agril. Univ. 17(2): 258–264, June 2019