American Journal of Water Resources, 2018, Vol. 6, No. 1, 1-8 Available online at http://pubs.sciepub.com/ajwr/6/1/1 ©Science and Education Publishing DOI:10.12691/ajwr-6-1-1 Trends in Climatic Variables and Their Impact on Crop Water Requirement and Crop Production Arpita Islam * , A.T.M. Hasan Zobeyer Department of Water Resources Engineering (DWRE), Bangladesh University of Engineering and Technology Dhaka, Bangladesh *Corresponding author: arpitaislam@wre.buet.ac.bd Abstract Climate change have innumerable potential effects on agricultural production which is a key economic sector in Bangladesh. Bogra, Rangpur and Rajshahi in the north-west region have been selected as the study area. This paper aims to investigate the combined effects of climatic variables on ETo and NIR and to estimate the yield of the crop Boro and Aman in these study area. For testing the statistical significance of trends in different agro-climatic variables both parametric and non-parametric methods are used. The results of the analysis reveal that maximum temperature has decreasing trends of 0.20c, 0.10c and 0.30c per decade at Bogra, Rajshahi and Rangpur station and relative humidity has increasing trends in most 10-day periods. Sunshine hour and solar radiation show decreasing trends and minimum temperature and wind speed show increasing trends. It is found that ETo has decreasing trends at Bogra, Rangpur and Rajshahi station which are 0.41, 0.35 and 0.15 mm/day respectively per decade. NIR shows decreasing trend of 0.0428, 0.021 and 0.0434 mm/day per decade at those stations respectively. Sensitivity analysis was done in terms of percentage change in temperature, wind speed, relative humidity and radiation to identify the relative importance of climatic variables on Eto. Though the temperature is increasing due to global warming and it has a positive effect on ETo and NIR, the changes in other climatic variables are more prominent than the changes in temperature which result in a decrease in ETo and NIR. Aqua Crop version 4.0 software was used to estimate the crop yield Boro and Aman at the three stations. At Rajshahi station yield of Boro and Aman is found to be 6.407 and 4.732 tons per hectare respectively. At Bogra station, yield of Boro and Aman is 6.407 and 3.66 tons per hectare. The yield of Boro is found to be 6.42ton per hectare at Rangpur station. These values are found to be relatively close to the values obtained from the Agricultural Statistics Report, 2011of BBS. Keywords: crop water requirement, evapotranspiration, boro, amon, aquacrop Cite This Article: Arpita Islam, and A.T.M. Hasan Zobeyer, “Trends in Climatic Variables and Their Impact on Crop Water Requirement and Crop Production.” American Journal of Water Resources, vol. 6, no. 1 (2018): 1-8. doi: 10.12691/ajwr-6-1-1. 1. Introduction Knowledge of crop-water requirements is crucial for water resources management and planning in order to improve water-use efficiency. Climate change is likely to affect agriculture in two distinct ways. One pathway is the direct effect of climate on crop growth and other pathway is through the supply of water for irrigation. So it is necessary to consider not only the direct effects of climate on crop yields but also on the effective water supply and the availability of water for agricultural users. Therefore the extent of this work covers the determination of various climatic variables such as rainfall, temperature, relative humidity, sunshine hour, solar radiation, wind speed etc and evaluate their combined on crop water requirement. The individual features and characteristics are analyzed and compared to establish a correlation in terms of climatic impacts on irrigational water requirement and the result is used in AQUACROP for crop production studies. The latest prediction from the fourth assessment report of' Intergovernmental Panel on Climate Change (IPCC, 2007) shows a median increase of 3.3 °C in annual mean temperature throughout the South Asia by the 21st century [1]. Karmakar and Shrestha (2000) reported that overall annual mean temperature of Bangladesh was likely to increase by 0.29°C and 0.39°C by 2050 and 2100 respectively [2]. Persson (1999) found an increasing trend in global radiation of 7.2% per decade within the BALTEX area or Swedendue to the decreasing cloudinessspecially in summer months [3]. The relative sunshine decreases of 0.18%, 0.19%, 0.22% at Shanghai, Nanjing and Hangzhou stations located in Eastern China every year, respectively, from 1961 to 2000 (Zhang et al., 2003) [4]. Ahmed et al. (2007) reported a significant increasing trend of annual relative humidity by a rate of 0.13 (%) per year from 1923 to 2005 at Amman Airport Meteorological (AAM) station of Jordan [5]. Tuller (2004) discussed trends in measured wind speed for four stations on the west coast of Canada and found decline in mean annual and winter wind speeds at Cape St James, Victoria International Airport, and Vancouver International Airport [6]. In India, Chattopadhyay and Hulme (1997) also found that increases in relative humidity and decreases in radiation are both correlated with the decreasing trend in potential evapo-transpiration [7]. Goyal (2004) suggested