Observed changes in extreme rain indices in semiarid and humid regions of Godavari basin, India: risks and opportunities

The present study examines the spatial and temporal changes in extreme rainfall events (EREs) across the Godavari river basin to develop adaptation strategies for vulnerable regions by understanding opportunities and risks. Indices such as consecutive dry and wet days, daily intensity, one-day highest precipitation, days with rainfall > 10 mm and 20 mm have been computed over the Godavari basin for the time period 1901–2015, and changes are compared between the two time periods 1901–1976 and 1977–2015. This study examines long-term trends on monthly and seasonal scales and climatological characteristics of EREs to understand the observed spatiotemporal changes in EREs. Analysis of EREs in the monsoon months further indicates significant trends over both traditionally “high-rainfall regions” (Humid) and “low-rainfall regions” (semiarid). In low-rainfall region, an increase in mean and coefficient of variability of annual rainfall has been identified during 1977–2015 as compared to pre-1977 period. It is also found that the month of September experienced statistically significant increase in frequency and intensity of all wet extreme rain indices during the period 1977–2015. Extremes in high- and low-rainfall regions show significant increase during 1977–2015 as compared to 1901–1976. Century scale analysis of extreme events with reference to regional level changes would help in looking at the grass root reality for the estimation of water budget as well as for developing region-specific adaptation measures and crop contingency plans. These findings would feed into state action plan for climate change to take appropriate measures to combat changing and rapidly occurring EREs in different climate zones of Godavari basin. Graphic abstract