Data | Learning from 2018 floods, here’s how Kerala managed dams better in 2022

Unlike 2018, the storage levels of dams and reservoirs were maintained better this year, using a concept called “Upper Rule Level”

Climate change is a clear and present danger globally and Kerala is no exception. The State’s monsoon pattern is shifting, with rainfall peaking in August instead of July in recent years. In 2018 and 2022, rainfall levels in August exceeded that of June and July on many days. However, there was minimal loss of lives and relatively much lesser flood damage compared to 2018 in the State. While it is true that the intensity of rainfall was relatively lower in 2022, the introduction of new dam management concepts, relying on global weather models apart from IMD predictions and improved communication with downstream flood measurement stations helped keep the reservoir levels in check and prevented river water from breaching the banks

In both 2018 and 2022, Kerala recorded copious amounts of rainfall on many days of August, exceeding the levels seen in June and July. This is a shift in the State’s rainfall pattern, as August, in general, receives lower rainfall, as suggested by the Long Period Average (LPA) which declines in August after June and July

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In 2018 and 2022, due to heavy August rainfall, the inflow of water to reservoirs also increased. In 2018, the inflows in August did not exceed the June-July levels. However, in 2022 it did. This shows that in 2022, a higher share of rainfall in August fell in the catchment area of the reservoirs, a crucial factor in flood management

The key difference between 2018 and 2022 was that, despite similar patterns of rainfall and comparable inflows, the storage levels of most dams and reservoirs stayed below the 90% mark in August this year. In 2018 however, the storage levels of most dams abruptly reached 100% in mid-August, leading to a catastrophe

If storage levels peak, the spills — excess water deliberately released from reservoirs — will rise. Unlike planned discharges, spills are not meant for specific utilisation such as irrigation. As storage levels of most dams remained below the 100% mark in 2022, the spills were sporadic unlike in 2018. This proved to be the crucial difference

As per the Central Water Commission, levels in 13 of the 44 flood monitoring stations across Kerala recorded an Extreme Flood Situation in 2018. The table on the right lists the name of the rivers and the measuring stations where the Extreme Flood Situation was recorded in 2018. Such a situation arises when a river exceeds the previously set Highest Flood Level (HFL) in that station in its history. In other words, in 2018, 13 stations recorded record-level of floods. In 2022, none of the 44 flood measuring stations witnessed an Extreme Flood Situation