Tracing Moisture Flow from the Bay of Bengal and Arabian Sea with its Impact on Ganga Basin during Monsoonal Extremes

The Ganga Basin, a region vital for agriculture and water resources, is heavily influenced by monsoonal rainfall patterns. Understanding the sources of this rainfall and their role in extreme weather events is critical. This study investigates the transport and contribution of moisture from two major sources the Bay of Bengal and the Arabian Sea on extreme rainfall events in the Ganga Basin from 2012 to 2023. We focus on analyzing the dynamics of moisture flow and the contributions of these sources during periods of heightened rainfall caused by cyclonic systems and other meteorological factors. Using a Lagrangian trajectory model, we track moisture fluxes and quantify water vapor transport from both the Bay of Bengal and the Arabian Sea. Our findings highlight the pivotal role of the Bay of Bengal in the Ganga Basin's rainfall, particularly during monsoon extremes. The Bay of Bengal's proximity to the Ganga Basin and its larger surface area make it the primary moisture source. The moisture generated in the Bay, aided by the monsoon winds, moves inland, directly influencing the seasonal and extreme rainfall patterns over the region. Additionally, cyclonic activity such as tropical storms and depressions further intensifies moisture transport, causing localized flooding and extreme rainfall events that alter the regular monsoon cycle. While the Arabian Sea does contribute to the Ganga Basin’s rainfall, especially during specific monsoonal periods, its influence is more intermittent and weaker compared to the Bay of Bengal. Moisture transport from the Arabian Sea is less direct, with its contributions more noticeable during particular timeframes, outside the peak monsoon season. This study provides a comprehensive understanding of how moisture recycling within the Ganga Basin interacts with moisture fluxes from the Bay of Bengal and the Arabian Sea. We assess how much each of these moisture sources influences extreme rainfall events, revealing the interconnectedness between the Ganga Basin’s moisture recycling processes and the external moisture inputs. This analysis is crucial in understanding the dependency of the Ganga Basin’s rainfall on these external moisture sources, as well as their combined contribution to extreme rainfall events. By examining these dynamics, the study contributes to a more precise understanding of the mechanisms that drive extreme rainfall in the Ganga Basin. It highlights the critical role of the Bay of Bengal in sustaining rainfall, especially during periods of heightened rainfall intensity, and offers insights into how these moisture sources affect the region’s water availability and agricultural productivity.