In the first 20 days of October 2021, every district in Kerala received more than 250mm of rainfall. In 10 of the 14 districts, rainfall received in October was twice the Long Period Average (LPA). As rainfall increased, water inflow to reservoirs also increased in October, swelling their storage to very high levels. Heavy to very heavy rainfall (64.5mm to 204.4mm) is predicted for Pathanamthitta, Kottayam and Idukki districts on Thursday. Therefore, inflows into major reservoirs in these districts and the resulting spills (excess water deliberately released from reservoirs) have to be closely monitored.
Pouring down
The graph shows the actual rainfall received in the first 20 days of October 2021 and the % departure from the LPA in every district of Kerala.
Chart 1 Actual rainfall and % from LPA Kerala rainfall
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Five year highs
The table compares rainfall received between October 1 and 20, 2021 with the five previous Octobers. For instance, in Ernakulam, 457.9 mm of rainfall was received between October 1 and 20, 2021, which is 196% of the rainfall received in October 2020 and 77% of October 2019. October 2019 was the wettest October between 2016 and 2020 in 13 districts.
Chart 2 Rainfall received in Octobers Kerala rainfall
Rising inflows
The graph shows the daily inflow of water into major reservoirs. The inflow has increased gradually in October, especially in the Idukki and Pamba reservoirs. The districts in which they are located are expected to receive heavy to very heavy rainfall on Thursday. Hence, inflows may increase further.
Chart 3 daily inflow in reservoirs Kerala rainfall
Dam watch
The storage levels (%) of all major reservoirs have surged in October. As of October 19, all of them crossed the 90% mark. Planned spills have already been initiated in the Pamba and Idukki reservoirs. Unlike discharges, spills are not meant for specific utilisation.
Chart 4 storage level of reservoirs Kerala rainfall
Source: IMD, Kerala State Electricity Board
Also read: Analysis | Kerala yet to get its basics right on tackling natural disasters
