Statistical analysis of rainfall in Bihar

Availability of water is largely dependent on the amount of precipitation received by an area. Fluctuations in precipitation pattern exercises significant impact on the livelihood of the people especially in areas where rainfed agriculture has predominance. In the present study, temporal variation of rainfall in Bihar, India has been analysed. Trend analysis for monthly, seasonal as well as annual rainfall series for the duration of 1950-2016 was performed using non-parametric Mann-Kendall. Parametric linear regression test was also used to check the trends. Deficiency in yearly total rainfall was identified using Index of Wetness and standardized rainfall anomaly. Precipitation Concentration Index (PCI) was also estimated to check the monthly distribution of rainfall. Both parametric and non-parametric tests predict declining trend in rainfall for almost all the months except for the month of May, which is reflected as a decline in total annual rainfall in the study area. Analysis of rainfall data revealed very high intra and inter annual variability [average coefficient of variation (CV)=91.26]. PCI values too revealed very high nonuniformity of rainfall. Analyses of data confirmed high concentration (84%) of rainfall in monsoon months. Rainfall depth with 90% dependability has been found to be over 180 mm and 160 mm for the months of July and August, respectively. Significant decline has been observed in total rainfall over the last three decades (1986-2016) highlighting the need of rainwater harvesting and management to avoid acute shortage of water in near future.