1Indian Institute of Technology, Roorkee-247667, Uttarakhand
2Indian Institute of Remote Sensing, Dehradun-248001, Uttarakhand
3Arba Minch University, Arba Minch-21, Ethiopia
*E-mail: radheyindia@hotmail.com
Online published on 12 January, 2018.
An attempt has been made in the present study to analyse the variability and trends in annual and seasonal rainfall over Eastern Ganga Canal (EGC) command area, India. The daily gridded (0.25,° x 0.25°) rainfall dataset prepared by the India Meteorological Department (IMD), Pune is used in the present study for the time period 1901–2012. Total 12 grids of IMD rainfall data covering entire command and surrounding area were selected for analysing the trend. To determine the trend in annual rainfall, seasonal rainfall, annual number of rainy days and seasonal number of rainy days, the non-parametric Mann-Kendall (MK) and Sen's methods were used. It has been observed that annual and monsoon rainfall has decreasing trend in grids 6, 7, 12 whereas, no significant trend has been observed in other grids (1, 2, 3, 4, 5, 8, 9, 10, 11). Similarly increasing trend was observed in grids 5, 9, 10 in case of annual rainy days, whereas, grids 6, 7, 8, 12 exhibits decreasing trend. In case of number of rainy days in monsoon season, decreasing trend has been observed in grids 6, 7, 12 with increasing trend only in grid 5 and no significant trend in remaining grids (1, 2, 3, 4, 8, 9, 10, 11). In general, the results of trend analysis revealed a decreasing trend in annual and monsoon rainfall in the range of 18.5 to 61.7 mm decade−1 and 19.4 to 56.7 mm decade−1, respectively. Decreasing trend of 1.8 to 2.9 days decade−1 was observed in some parts of the command area in annual rainy days, whereas some part showed increasing trend in the range of 0.2 to 1.4 days decade−1. In case of number of rainy days in monsoon season, the decreasing trend varies from 1.4 to 2.2 days decade−1 whereas the increasing trend in grid 5 is 1.0 days decade−1. The variability analysis has also been performed to highlight the frequency of dry and wet years. The coefficient of variability of annual rainfall, seasonal rainfall, annual number of rainy days and number of rainy days in monsoon ranges from 0.24 to 0.31, 0.29 to 0.38, 0.14 to 0.21 and 0.20 to 0.27, respectively. Analysis for dry year and wet year on annual scale were carried out for command area, which showed that there are 18 dry years and 21 wet years within 1901 to 2012. The driest year and wettest year were 1987 and 1942, respectively
Eastern Ganga canal command, Man-Kendall test, Rainfall trend, Rainfall variability, Sen's slope estimator
