Trends in Rainfall Pattern over Eastern Ganga Canal Command

The climate change has affected the rainfall characteristics worldwide. However, the changes are not similar for all areas and have localized magnitude, so must be quantified locally to optimally manage the natural resources. In developing countries like India rainfall is the main source of water for agriculture. Even in areas with irrigation facilities, the irrigation supplies are designed to fulfill the deficit between natural water available to the crops (e.g. rainfall) and the crop water requirement. So the knowledge of total seasonal and annual rainfall available in the region will help in planning and management of the available water resources. Keeping this in mind an attempt has been made in the present study to analysis the trends in annual and seasonal precipitation over Eastern Ganga Canal (EGC) command area, India during past century (1901-2012). To determine the trend in annual as well as monsoonal rainfall and number of rainy days, the non-parametric Mann-Kendall and Sen's methods were used. Annual average rainfall in the region varies from 919.57 to 1558.08 mm/year, with the weighted average rainfall of 1165.93 mm/year for entire command area. A total of 77.36% of total annual rainfall occurs in monsoon season. Monsoon rainfall varies from 722.39 to 1198.32 mm/year within 12 grids, with the weighted average monsoon rainfall of 901.95 mm/year for all grids. Annual number of rainy days in EGC command varies from 53 to 93 days (with the mean of 66 days), out of which 34 to 60 days were spread in monsoon season, with a weighted average of 41 rainy days in monsoon. It has been observed that annual and monsoon rainfall have decreasing trend in grids 6, 7, 12 whereas, no significant trend has been observed in other grids. While, for annual rainy days, the increasing trend has been observed in grids 5, 9, 10 and decreasing in grids 6, 7, 8, 12; and no significant trend has been observe in grids 1, 2, 3, 4, 11.