Challenges
Pollution Threats and Impacts
Pollution remains one of the most significant threats to Vembanad Lake. Industrial effluents contribute around 60% of the pollution load (Kumar et al., 2017), while agricultural runoff has increased by 150% over the last two decades (Kerala State Pollution Control Board, 2021). Untreated domestic sewage accounts for another 40% (CWRDM), compounded by waste from tourism activities. These pollutants exacerbate eutrophication, causing nutrient overloads and algal blooms that disrupt the lake’s ecological balance.
The Kuttanad region’s use of fertilizers (20,000 tons annually) and the presence of agrochemicals and pesticides (Kerala State Pollution Control Board, 2010) significantly contribute to nutrient enrichment and further eutrophication. The runoff carries these chemicals into the lake, compromising water quality and altering the ecosystem (Padmakumar, 2006).
Industrial discharges, including untreated effluents from factories like the McDowell distillery in Cherthala, fail to meet the Central Pollution Control Board (CPCB) standards and add to organic pollution, harming aquatic habitats and reducing biodiversity (Lekshmi and Jaya, 2006). Urbanization, especially around Alappuzha, has further intensified water pollution, with projections indicating that urban sewage in the catchment area will reach 92.75 million liters per day by 2034, along with approximately 187 tons of solid waste daily (Remani et al., 2010). Much of this waste comes from houseboats discharging untreated sewage and kitchen waste directly into the lake, raising coliform bacteria levels and posing significant health risks (S Beevi and V Devadas, 2014).
Sedimentation and Reduced Capacity
Over time, Vembanad Lake’s area has shrunk from 365 to 206 square kilometers, largely due to sedimentation caused by upstream deforestation and monoculture plantations. This reduction in size and depth has decreased the lake’s water-holding capacity, making it more vulnerable to flooding, especially during the monsoon season.
The Thanneermukkom Barrage, initially built to prevent saltwater intrusion and enhance agricultural productivity, has exacerbated sedimentation by blocking natural tidal flows. Sediment now settles within the lake, reducing its average depth and water retention capacity, further contributing to frequent flooding and deteriorating water quality.
Impact on Biodiversity
The combined effects of pollution and sedimentation have severely impacted Vembanad Lake’s biodiversity. Since 1993, the bird population has declined by 40%, with migratory ducks no longer roosting in the area (Vembanad Water Bird Count, 2003). The overgrowth of invasive aquatic plants like water hyacinth worsens water stagnation, making it difficult for native species to thrive. Fish populations have also declined by 30% due to habitat loss and reduced water quality (ICAR, 2017). Heavy metal contamination from industrial effluents accumulates in aquatic organisms, posing health risks to both wildlife and humans (Kumar et al., 2017).
Urbanization and Tourism
The rapid urbanization around Vembanad Lake, particularly in Alappuzha and Cherthala, has led to increased pollution levels. The expanding urban areas contribute to untreated sewage and solid waste entering the lake, while the growth of houseboat tourism exacerbates pollution. Waste from houseboats, including sewage and kitchen waste, is often discharged directly into the lake, raising coliform bacteria levels, particularly around houseboat jetties (S Beevi and V Devadas, 2014). The influx of tourism has put additional pressure on waste management systems, which are often inadequate.
The regions of Muhamma, Mannanchery, and Aryad, currently less developed, are expected to urbanize in the future, further contributing to pollution. The combined impact of urbanization, tourism, and inadequate waste management systems poses a significant threat to the lake’s ecosystem.
Urbanization and Tourism
The rapid urbanization around Vembanad Lake, particularly in Alappuzha and Cherthala, has led to increased pollution levels. The expanding urban areas contribute to untreated sewage and solid waste entering the lake, while the growth of houseboat tourism exacerbates pollution. Waste from houseboats, including sewage and kitchen waste, is often discharged directly into the lake, raising coliform bacteria levels, particularly around houseboat jetties (S Beevi and V Devadas, 2014). The influx of tourism has put additional pressure on waste management systems, which are often inadequate.
The regions of Muhamma, Mannanchery, and Aryad, currently less developed, are expected to urbanize in the future, further contributing to pollution. The combined impact of urbanization, tourism, and inadequate waste management systems poses a significant threat to the lake’s ecosystem.