ORIGINAL PAPER Assessing recent impacts of climate change on design water requirement of Boro rice season in Bangladesh ARM Towfiqul Islam 1,2 & Shuanghe Shen 1,3 & Shenbin Yang 1,3 & Zhenghua Hu 1,3 & Ronghao Chu 3 Received: 9 January 2017 /Accepted: 15 February 2019 # Springer-Verlag GmbH Austria, part of Springer Nature 2019 Abstract Water requirement is sensitive to the impacts of climate change, especially in Bangladesh because of limited freshwater avail- ability in the dry season, despite the fact that the country’ s agriculture sector requires large quantities of water for the crop production. Hence, gaining a better understanding of changes in water requirements in Bangladesh during dry periods is important in the management of agricultural water resources. This study assesses the recent impacts of climate change on the design water requirement (DWR) of the Boro rice–growing season in Bangladesh using a frequency analysis over a 5-year period. The reference evapotranspiration (ET ref ), crop evapotranspiration (ET p ), effective rainfall (ERF), and gross irrigation water requirements (GIWR) of Boro rice were estimated based on daily weather data for the period of 1984–2013 using the CROPWAT8.0 model. The results showed the significant decreasing trends of ET ref in most of these Boro rice growth stages in all districts. The GIWR of Boro rice and its trends demonstrated significant spatial heterogeneity in the last three decades due to significant changes in the ERF and ET p . The DWR of Boro rice–growing season also supported the results of the GIWR, and the Weibull probability distribution function (PDF) is found to be an optimal PDF among eight PDFs for the estimation of DWR. Overall, the results indicate that a recent climate change does not only contribute to high water demands for the crop but also result in decrease water requirements due to variations in wind speed, sunshine hours, and relative humidity. 1 Introduction The ongoing climate change and its multi-dimensional impact on crop production and agricultural water resource manage- ment have become a major challenge which Bangladesh will have to cope with in the twenty-first century (Ruane et al. 2013). According to the Intergovernmental Panel on Climate Change (IPCC), in the past 100 years, mean air temperature has increased by 0.6–1.06 °C globally and by 0.2–0.3 °C in Bangladesh (IPCC 2014). The global climate is changing and Bangladesh is one of the most vulnerable countries because of the effects of anthropogenic climate change (IPCC 2007). The effects of climate change in the irrigation sector will probably be a critical issue for Bangladesh due to increased risk of the dry season drought events (Agrawala et al. 2003). An assess- ment of recent climate change effects on the water require- ment of crops is vital for water resource management in Bangladesh. Recent impacts of climate change on the water requirement of global or basin scales are not comprehensive enough for understanding the results of regional climatic var- iations in a region. In such cases, a regional study is essential to show the consequence of a recent climatic change in water resource management perspective (Woznicki et al. 2015). Furthermore, trends of water demand have been investigated from historical daily weather data and compared to the trends of local meteorological variables, which can provide an un- derstanding of climate-induced changes in the water require- ment under recent water management scenarios. Irrigation for rice production is the highest water user sec- tor in Bangladesh (Acharjee et al. 2017). The total irrigation requirement of Bangladesh in 2010 was estimated at 33 km 3 , Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00704-019-02818-8) contains supplementary material, which is available to authorized users. * ARM Towfiqul Islam Towfiq_dm@brur.ac.bd 1 Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science and Technology, Nanjing 210044, China 2 Department of Disaster management, Begum Rokeya University, Rangpur 5400, Bangladesh 3 School of Applied Meteorology, Nanjing University of Information Science & Technology, Nanjing 210044, China Theoretical and Applied Climatology https://doi.org/10.1007/s00704-019-02818-8