Attribution of hydrometeorological variability in flood generation over the Godavari River

Understanding of flood generating mechanisms is necessary for the largely populated Indian Subcontinent, which observes frequent floods in the large river basins during the Asian monsoon. However, the flood processes linked with the hydrometeorological variability remain unexplored over India. This study examines temporal and spatial variability of hydrometeorological variables (precipitation and surface runoff) prior to large streamflow events to identify the dominated flood processes and contributing areas in the Godavari river basin, the second largest basin in India, using the observed and model-simulated data. Based on the temporal variability in precipitation and surface runoff, we find that long-rain type floods predominantly occur in the semi-humid region of the Godavari basin (Tekra, Pathagudam, Peur, and Polavaram sub-basins). These floods are associated with the long-duration (10-11 days) accumulated precipitation due to the occurrence of multiple high-intensity precipitation events prior to flood. However, floods in the semi-arid Mancherial sub-basin are linked with the short-duration (2-days) accumulated precipitation with single high-intensity precipitation. Apart from temporal variability of hydrometeorological variables, we also analyzed the spatial variability of precipitation and runoff prior to flood events using the empirical orthogonal functions (EOF) analysis. We show that the central and downstream regions of the Godavari basin contribute more in the flood occurrence. Moreover, our analysis shows that the Tekra basin generates more runoff before the flood events compared to the other basins due to the favorable catchment conditions. Overall, our study provides a better understanding of flood processes over a large river basin of the Indian Subcontinent during the monsoonal climate, which can be used for numerous flood control and management applications.