Regional scale trend and variability of rainfall pattern over agro-climatic zones in the mid-Mahanadi river basin of eastern India

Abstract

Investigation of trends and variability in rainfall patterns is of paramount importance for the effective planning and management of rainfed cropping systems. In this study, a detailed analysis is carried out to understand the changes in rainfall patterns and characteristics at a regional scale on agro-climatic zone basis, in the mid-Mahanadi river basin. Daily rainfall data of India Meteorological Department (IMD) at 0.25° × 0.25° spatial resolution has been analyzed for the period of 1979–2013 on a monthly, seasonal, and annual timescale to investigate variability, trends, and seasonality of rainfall. Results of analysis reveal that there is large spatio-temporal variation in the river basin with a shift in seasonality of rainfall, with increased prolonged dry spells, and significant increase in extreme weather events over the agro-climatic zones (AZ). Most of the agro-climatic zones are found to have significant decreasing trends in the magnitude of rainfall during the non-monsoon season. In particular, agro-climatic zones nearer to the coastal region are more vulnerable to the high rainfall, whereas the North-Eastern-Ghat (AZ67) and Western-Central-Table (AZ68) regions are susceptible to the moisture stress. Further, analysis of groundwater level fluctuation shows a significant decline in groundwater level during the monsoon as well as non-monsoon seasons. The resulted effect of rainfall variability can be seen in terms of an increase in the prolonged dry spells as well as decline in the groundwater level. Moreover, the results of this study indicate a climate change signal at the regional scale that will help the policymakers and water managers to identify the critical agro-climatic zones in the mid-Mahanadi river basin for the formulation of efficient water resources management and planning strategies, particularly for the major crops of the rainfed agriculture regions.