South India is bracing for an early arrival of the northeast monsoon, marking the second consecutive year of this phenomenon in Tamil Nadu. Forecasters predict another season of significantly higher-than-average rainfall, mirroring last year’s 33% surplus, which could lead to complex challenges for the region.
For years, authorities have viewed abundant rainfall as a boon. However, climate change is altering this perspective. While overall rain volumes are rising, the precipitation often occurs in intense, localized downpours. This delivers excessive water to areas ill-equipped to absorb it, making it crucial to rethink the traditional belief that ‘more rain is always better.’
City landscapes, dominated by concrete and asphalt, can’t absorb heavy rainfall effectively. This leads to rapid runoff that overwhelms drainage systems, causing flash floods, submerged low-lying areas, property damage, and transportation disruptions. We saw this during Cyclone Michaung in Tamil Nadu in 2023, where power was cut due to fears of loose cables. Moreover, the sheer volume of water can trigger sewage overflows, releasing untreated wastewater into streets and water bodies, creating serious health and environmental risks.
Excessive rainfall poses a severe threat to agriculture. Waterlogged soil can suffocate plant roots, wash away valuable seeds and young crops, and gradually strip away nutrient-rich topsoil, diminishing long-term fertility. High moisture levels also create ideal conditions for fungal diseases and pests, which can decimate harvests and cause substantial financial losses for farmers. Furthermore, intense downpours can carry fertilizers, pesticides, and other farm waste into reservoirs and other water bodies, polluting vital water sources. Stagnant water, a common consequence, becomes a perfect breeding ground for mosquitoes, elevating the risk of vector-borne diseases like malaria and dengue, as well as zoonotic diseases such as leptospirosis, Japanese encephalitis, and scrub typhus.
Extended periods of rain also cause the water table – the point at which the ground is saturated – to rise. A consistently high water table can threaten the stability of building foundations, roads, and other crucial infrastructure. It can also exert pressure on basement walls, leading to cracks, leaks, and even mold growth. Moreover, saturated soil loses its ability to bear weight, causing foundations to shift or settle, which can result in severe structural damage over time.
The combined effects of these problems result in substantial economic and social burdens. Repairs to damaged buildings, public infrastructure, and agricultural lands require massive investments. Business and transportation disruptions severely hinder economic activity. Floods and landslides can displace entire communities, cause injuries, and tragically, even fatalities, especially among vulnerable populations. The emotional toll on those affected, including stress and anxiety, is another critical yet frequently ignored consequence.
Tamil Nadu must also account for the ‘Kerala factor.’ These two states experience distinct monsoon patterns: Kerala receives its main rainfall from the southwest monsoon (June-September), while Tamil Nadu relies on the northeast monsoon (October-December). A critical issue emerges when these monsoon seasons overlap or when both states simultaneously face heavy rainfall, a scenario currently unfolding with the early onset of the northeast monsoon.
Central to this issue is the Mullaperiyar Dam. Although situated in Kerala’s Idukki district, the dam is managed by the Tamil Nadu government, diverting water for irrigation to districts like Theni, Madurai, and Dindigul. This creates a direct connection between rainfall in Kerala’s catchment areas and the water levels in Tamil Nadu’s river systems.
When the Mullaperiyar Dam’s catchment areas experience heavy rainfall, the reservoir quickly reaches its capacity. To maintain the dam’s safety and manage water levels, Tamil Nadu’s authorities must open its shutters, releasing a vast amount of water downstream. This released water divides, creating a dual challenge: one portion flows into Kerala’s Periyar River, threatening floods in Idukki district and escalating an inter-state dispute, while the main flow is diverted to Tamil Nadu’s Vaigai Dam. This influx often coincides with Tamil Nadu’s own rivers and reservoirs already being full from its ongoing northeast monsoon.
This overlapping influx transforms Kerala’s ‘surplus’ water from a potential asset into an immediate flood threat for Tamil Nadu. Beyond managing its own rainfall, Tamil Nadu now faces the challenge of handling a massive, concentrated water inflow from its neighboring state. Currently, all 13 shutters of the Mullaperiyar Dam are open, releasing thousands of cusecs of water to accommodate the continuous deluge. Consequently, agricultural land and residential areas in Theni are already underwater, even as the district endures its own monsoon downpours.
For these critical reasons, it’s becoming clear that both Tamil Nadu and Kerala, along with other affected states, must urgently re-evaluate the long-held belief that ‘excess rainfall is good rainfall.’