For the second year in a row, the northeast monsoon has arrived early in Tamil Nadu, gracing the region at least four days ahead of schedule. Last year, this monsoon phase delivered a remarkable 33% more rainfall than the long-term average, and experts are predicting a similar pattern for this year.
Traditionally, both government officials and state authorities viewed abundant rainfall as a blessing. However, climate change is dramatically altering this perspective. While overall rainfall amounts may be rising, the precipitation often comes in intense, localized downpours. These sudden deluges deliver far too much water for affected areas to effectively absorb, forcing a crucial re-evaluation of the long-held belief that ‘more rain is always better.’
In bustling urban centers, expansive concrete and asphalt surfaces prevent heavy rainfall from permeating the ground. This leads to swift runoff that quickly overwhelms existing drainage systems, triggering flash floods, inundating low-lying areas, causing property damage, and disrupting vital transportation networks. Recalling events like Cyclone Michaung in Tamil Nadu during 2023, city power authorities frequently resort to cutting electricity, often citing concerns about loose cables. Furthermore, the sheer volume of water can cause sewage systems to overflow, discharging untreated wastewater directly into streets and natural water bodies, posing severe health and environmental risks.
The agricultural sector is acutely susceptible to heavy rainfall. Waterlogged soil can suffocate plant roots, wash away precious seeds and young crops, and gradually erode nutrient-rich topsoil, diminishing long-term fertility. Excessive moisture also fosters the rapid spread of devastating fungal diseases and pests, leading to significant crop losses and substantial financial hardship for farmers. Additionally, intense downpours can carry fertilizers, pesticides, and other agricultural waste into crucial water bodies, including reservoirs, severely compromising water quality. Lastly, standing water creates ideal breeding grounds for mosquitoes, increasing the prevalence of vector-borne illnesses like malaria and dengue, alongside zoonotic diseases suchch as leptospirosis, Japanese encephalitis, and scrub typhus.
Extended periods of heavy rainfall also lead to a rise in the water table, the subsurface level where the ground is fully saturated. A consistently high water table can severely jeopardize the stability of building foundations, roads, and other critical infrastructure. It can exert immense pressure on basement walls, causing cracks, leaks, and fostering mold growth. Furthermore, saturated soil loses its crucial load-bearing capacity, potentially causing foundations to shift or settle and leading to considerable structural damage over time.
The combined effect of these challenges results in substantial economic and social costs. Extensive damage to buildings, public infrastructure, and agricultural land necessitates massive investments in repair and reconstruction. Widespread disruptions to businesses and transportation networks severely impede economic activity. Flooding and landslides can also displace entire communities, cause injuries, and tragically, even fatalities, especially among vulnerable populations. The profound psychological impact on affected individuals, manifesting as stress and anxiety, represents another crucial, yet frequently underestimated, consequence.
Tamil Nadu faces a unique challenge, particularly when considering the ‘Kerala factor.’ These two states experience distinct monsoon patterns: Kerala primarily relies on the southwest monsoon from June to September, while Tamil Nadu receives the bulk of its rainfall during the northeast monsoon, which spans from October to December. A significant issue emerges when these monsoon cycles overlap, or when both states simultaneously endure intense rainfall – a scenario currently unfolding with the early arrival of the northeast monsoon.
Central to this complex situation is the Mullaperiyar Dam. Although situated within Kerala’s Idukki district, the dam is managed by the Tamil Nadu government, serving to divert water for irrigating agricultural lands in Theni, Madurai, Dindigul, and surrounding districts. Consequently, there’s a direct and critical correlation between rainfall in Kerala’s catchment areas and the water levels within Tamil Nadu’s river systems.
Heavy rainfall in the Mullaperiyar Dam’s catchment areas causes the reservoir to fill quickly. To maintain dam safety and control surging water levels, Tamil Nadu’s authorities are obligated to open the dam’s shutters, unleashing a substantial volume of water downstream. This released water flows in two directions, creating a dangerous ‘double whammy.’ One stream courses down Kerala’s Periyar River, potentially flooding Idukki district’s low-lying regions and sparking inter-state tensions. Simultaneously, the main flow is diverted to Tamil Nadu’s Vaigai Dam. This fresh influx can arrive precisely when Tamil Nadu’s own rivers and reservoirs are already brimming from the ongoing northeast monsoon.
This synchronized deluge transforms Kerala’s ‘excess’ water from a potential asset into an immediate flood crisis for Tamil Nadu. Instead of merely managing its internal rainfall, Tamil Nadu must also contend with a vast, concentrated inflow from its neighboring state. Currently, all 13 shutters of the Mullaperiyar Dam remain open, releasing thousands of cusecs of water to accommodate the continuous inflow. Consequently, farmlands and residential zones in Theni are already submerged, even as the district grapples with its own relentless monsoon rains.
Considering these critical factors, it’s increasingly evident that both Tamil Nadu and other states facing similar scenarios, including Kerala, must fundamentally re-evaluate the traditional wisdom that ‘excess rainfall is always beneficial.’