Analysis of Rainfall Trend before and after Implementation of Eastern Ganga Canal Command

摘要

Huge number of irrigation projects are planned and executed throughout the globe for boosting agricultural production. However, in many of the irrigation projects the problem of efficient water management is becoming more complex with every passing year. The main reason for this may be the changing trends of water availability and demand, which is mainly dependent on precipitation. Though the irrigation projects are designed considering long-term historical climatic conditions, however, the accelerated climatic shift and change has put forward situations which were unimaginable in the past. Keeping this as background, in the present study, rainfall trend analysis has been done over the command area of Eastern Ganga Canal (EGC) command for both pre project implementation phase (1901-1970) and post project implementation phase (1971-2012). Daily rainfall data of 102 years has been analysed using the non-parametric Mann-Kendall and Sen's methods to highlight the trends in annual, seasonal rainfall and number of rainy days. Analysis result showed increasing trend of 0.93 mm/year and 2.03 mm/year in annual rainfall and monsoon rainfall respectively, in the pre-project implementation phase, while decreasing trend of 0.27 mm/year and 1.11 mm/year in annual rainfall and monsoonal rainfall, respectively, in post-implementation phase has been observed. Further, occupancy of dry years was analysed using five year moving average analysis. The results indicated increase in probability of occurrence of dry years in pre to post project implementation phase from 7.1% to 14.3%. These results will help project managers in development of alternative management strategy.