Erratic monsoon after-effects loom large over India

India has had a quite a monsoon season this year. As of October 19, the Southwest monsoon season gave way to the northeast monsoons. However, the erratic nature and underperformance of the monsoons so far have left the country rather dry, and this could be a grave concern during next year’s summer season, according to the Weather Channel India (WCI) as it asks if Indian reservoirs have enough water to sustain demand in the coming months.

A WCI report states that between June 1 and September 30, India saw below-normal rains that led to a countrywide cumulative deficiency of 5.6% compared to the long-period average for the season. You might think the situation must have improved in October, but since the beginning of this month, the country has witnessed a concerning shortfall of 18%. The previous week was particularly hard on India, and most parts of the country saw deficient to no rainfall. Naturally, this has taken a toll on the country’s water supplies. Water levels in 150 key reservoirs in India dropped to 73% of the 178.784 billion cubic metres (BCM) capacity this week.

The report adds that as of October 19, 2023, these reservoirs held 129.636 BCM of water, which is 19% less than last year (when they held 160.400 BCM) and 8% lower than the ten-year average of 140.280 BCM. Water levels have dropped considerably in every single region compared to the previous year. Regional variations highlight differences in water storage levels, as per the report. The states having less water than the previous year include Himachal Pradesh, Punjab, Rajasthan, Odisha, Nagaland, Tripura, Maharashtra, Uttar Pradesh, Madhya Pradesh, Chhattisgarh, Telangana, Andhra Pradesh, Karnataka, Kerala and Tamil Nadu. But a few states like Assam, West Bengal, Bihar, Gujarat and Uttarakhand boast better storage than last year for the corresponding period. As for the basins in various regions, better than normal water levels were seen in the Ganga, Subarnarekha, Brahmani and Baitarani, West flowing rivers of Kutch-Saurashtra like Luni, Narmada, Tapi, Mahi and Sabarmati.

However, deficient levels were recorded in east-flowing rivers. While the southern and eastern states still stand a good chance of having their reservoirs filled to the brim with the winter monsoon’s aid, the other parts may not be as lucky.

This could have significant implications on agriculture, drinking water availability, as well as the power sector, as 20 of the 150 major reservoirs in the country are dedicated to hydroelectric projects.

A few days earlier, the WCI had also reported that the India Meteorological Department (IMD) had highlighted cyclonic circulations showing that this year’s first post-monsoon cyclone would be forming in the Arabian Sea, and not the Bay of Bengal.

Cyclone Tej is now the third cyclone of 2023, after Cyclone Mocha over BoB in May and Cyclone Biparjoy over the Arabian Sea in June. Tropical cyclones developing in the Bay of Bengal and the Arabian Sea are a common occurrence before and after the Indian summer monsoon – between April-May and October-December because of the difference in wind patterns and sea surface temperatures. During the southwest monsoon, strong winds blowing from the southwest help to suppress the formation of cyclones. After the monsoons, however, wind patterns turn more favourable. And warmer ocean temperatures between October to December act as fuel for cyclogenesis in the Bay of Bengal and the Arabian Sea.

Until now, as this WCI report points out, it was usually the Bay of Bengal that saw the first post-monsoon cyclone. In fact, in 2022, the Arabian Sea saw no cyclones between October and December while the Bay of Bengal witnessed two tropical storms in this duration – Sitrang and Mandous.

But the rising global sea-surface temperature mean increasingly unusual activities! In 2029, for instance, the Arabian Sea witnessed an unprecedented five cyclones, four of whom – Hikka, Kyarr, Maha, Pawan – formed post-monsoon.

The retreating southwest monsoon winds also usually push the systems forming in the Arabian Sea to the western side, pushing most cyclones that are forming towards the Middle Eastern countries. However, there are exceptions, and these cyclones occasionally change paths and take a detour towards Gujarat and Pakistan. Arabian Sea cyclones are turning increasingly unpredictable, the WCI report adds, saying that experts believe that climate change might be playing a role here and the increase in cyclonic activity could be due to rising ocean temperatures and increased availability of moisture under global warming.