For the second year in a row, the northeast monsoon has arrived early in Tamil Nadu. Last year, this monsoon brought 33% more rainfall than the long-term average, and meteorologists anticipate a similar trend this year, indicating another season of potentially heavy rains.
Traditionally, both government officials and local authorities have viewed abundant rainfall as a blessing. However, climate change is shifting this perspective. While overall rainfall amounts may be higher, the rain often falls in intense, localized downpours. This delivers too much water too quickly to areas that cannot fully absorb it, leading to a critical need to re-evaluate the perception that ‘more rain is always better.’
Cityscapes, dominated by concrete and asphalt, prevent natural water absorption. This results in rapid runoff, overwhelming drainage systems and causing flash floods, submerged low-lying areas, property damage, and transportation chaos. During severe weather, like the event that affected Tamil Nadu in 2023, urban power providers often cut electricity due to concerns about loose cables. The immense volume of water also triggers sewage overflows, releasing untreated wastewater into streets and natural water bodies, which poses serious health and environmental risks.
The agricultural sector is highly susceptible to heavy rainfall. Waterlogged soil can suffocate plant roots, wash away newly planted seeds and young crops, and gradually erode nutrient-rich topsoil, diminishing long-term soil fertility. Excessive moisture also fosters the proliferation of fungal diseases and pests, which can decimate crops and reduce yields, leading to substantial financial hardship for farmers. Furthermore, powerful rain bursts can sweep fertilizers, pesticides, and other farm pollutants into waterways and reservoirs, compromising water quality. Lastly, standing water creates ideal breeding grounds for mosquitoes, elevating the threat of vector-borne illnesses like malaria and dengue, as well as zoonotic diseases such as leptospirosis, Japanese encephalitis, and scrub typhus.
Extended periods of heavy rain also cause the water table – the underground level where soil is saturated – to rise. A consistently high water table can jeopardize the stability of building foundations, roads, and other critical infrastructure. It can also exert considerable pressure on basement walls, resulting in cracks, leaks, and the proliferation of mold. Moreover, saturated soil loses its ability to bear weight, which can cause foundations to shift or settle, potentially leading to severe structural damage over time.
The combined effects of these problems incur substantial economic and social burdens. Repairs and reconstruction of damaged buildings, public infrastructure, and farmland require considerable financial outlay. Business interruptions and disrupted transportation networks hinder economic progress. Floods and landslides can also force communities to relocate, cause injuries, and tragically, even claim lives, especially among vulnerable populations. The emotional strain on those affected, including stress and anxiety, represents another profound, yet frequently underestimated, consequence.
Tamil Nadu must also account for the ‘Kerala factor’ in its rainfall management. These two states experience different primary monsoon seasons: Kerala relies on the southwest monsoon from June to September, while Tamil Nadu receives most of its rainfall during the northeast monsoon from October to December. A significant challenge emerges when these monsoon seasons overlap or when both states simultaneously face intense downpours, which is precisely what is happening with this year’s early arrival 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, which uses its waters to irrigate farmlands in districts like Theni, Madurai, and Dindigul. This creates a direct correlation between rainfall in Kerala’s catchment areas and the water levels within Tamil Nadu’s river systems.
When the Mullaperiyar Dam’s catchment areas receive heavy rainfall, the reservoir quickly reaches capacity. To ensure the dam’s structural integrity and control water levels, Tamil Nadu’s authorities are forced to open its gates, sending a substantial volume of water downstream. This released water divides, posing a dual threat. Part of it flows into Kerala’s Periyar River, potentially flooding Idukki district and becoming an interstate concern. The main flow, however, is diverted to Tamil Nadu’s Vaigai Dam. This influx often coincides with Tamil Nadu’s own rivers and reservoirs already being full from the ongoing northeast monsoon, exacerbating flood risks.
This synchronized surge transforms Kerala’s ‘excess’ water from a potential benefit into an immediate flood threat for Tamil Nadu. Instead of simply managing its own rainfall, Tamil Nadu is burdened with handling a vast and 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 relentless inflow. Consequently, farmlands and residential zones in Theni are already underwater, even as the district endures its own severe monsoon rains.
Given these circumstances, it is evident that states like Tamil Nadu and Kerala must urgently reassess the long-held belief that ‘excess rainfall is always beneficial.’