Assessment of regional-level long-term gridded rainfall variability over the Odisha State of India

Odisha State is located in eastern part of India which is blessed with sufficient amount of rainfall. Major part of the state is covered by Mahanadi river basin; Mahanadi river basin originated from Sihawa town and disposed out to Bay of Bengal near Sambalpur, Odisha State. The distribution pattern is erratic and uneven due to climate, topography, hydrology and geomorphology of the state. Catchment area of the Mahanadi is vast; therefore, drainage order is also high (about six); due to these features large amount of water has generated, and it will be appeared as flood at downstream through deltaic region to Bay of Bengal. In this connection, water resources planning and management are one of the crucial issues. For any hydrological study, it is necessary to identify the characteristics and climatic variability of the catchment. In the present study, long-term (1901-2013) rainfall time series has been utilized for rainfall variability analysis using nonparametric tests, viz. Mann-Kendall (MK), modified Mann-Kendall (MMK) and Theil-Sen's slope. The average annual rainfall of the Odisha State is to be found as about 1438mm; out of them, about 78% occurs in the monsoon season. In the present study, it was found that the maximum and minimum rainfalls occurred at Bhadrak and Puri districts, respectively. As per change point detection, it was found to be as 1945 is shift change year. Further, it was noticed that most of the districts are showing positive trends before change point and vice versa. Similar results are estimated in the monsoon season because most of the rainfall has occurred in the monsoon season. Both positive and negative trends have been found in Odisha State; detailed study has been carried out for rainfall behavior identification of the state. The present study is useful for agricultural and water resources planning and mitigation.