Varikoden, H.; Roja, C.; Revadekar, J.V., and Milind, M., 2020. Rainfall variation in major river basins in India and the association with the Indo-Pacific Oceans. In: Sheela Nair, L.; Prakash, T.N.; Padmalal, D., and Kumar Seelam, J. (eds.), Oceanic and Coastal Processes of the Indian Seas. Journal of Coastal Research, Special Issue No. 89, pp. 1-6. Coconut Creek (Florida), ISSN 0749-0208.
The summer monsoon rainfall is the major water source for most parts of India and people depend on this water source for their livelihood. The rainfall during this season is highly variable over space and time. The rainfall during the southwest monsoon period is the main source of flow discharge in most of the rivers in India. In the present study, we made an attempt to explore the variability and trends in rainfall over the Ganges, Brahmaputra, Godavari and Krishna river basins. Northern river basins show a negative trend indicating the decrease of rainfall and increasing trends are observed in peninsular river basins. The Brahmaputra river basin shows a significant decreasing trend (-0.16 mm day-1 decade-1). Moreover, the variability in multi-time scale is also different for different basins. Among all the river basins considered in the study, the Brahmaputra river basin registered high average rainfall (15.11 mm day-1 with a standard deviation of 2.23 mm day-1) and the Krishna river basin the least (3.57 mm day-1 with a standard deviation of 0.87 mm day-1). Further, the large scale teleconnection of the rainfall with individual river basins has also been assessed. The Ganga river basin is one of the largest river basins and this region is highly influenced by the Arabian Sea and the west Pacific Ocean (Nino 3.4 region). However, the Brahmaputra basin does not show much connection with Sea Surface Temperatures (SST) over the west Pacific Ocean, the Arabian Sea or the Bay of Bengal. The rainfall in the Godavari and Krishna river basins have more influence on SSTs over the central Pacific Ocean.