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<p>The fast degradation in bathymetry, floodwater retention capacity, and changes in salinity regimes of Vembanad—the largest wetland system in South India—and its impacts on the ecosystem services are assessed using high-resolution data sets on bathymetry and hydrography. Strengthening the outer banks of Kuttanad polders to promote paddy cultivation led to a sharp decline in its sediment (suspended) filtration potential, promoting heavy siltation and depth shrinkage of Vembanad Lake. With an area of 315 sq.km and an average depth of 8.5&#xa0;m (south sector)/7.87&#xa0;m (central sector), the lake had a retention capacity of 2617.5 MCM floodwaters in 1930 which was reduced to 384.7 MCM by 2020 (85.3% loss in retention capacity) due to area (162.5 sq.km) and depth (average 1.8&#xa0;m in the south sector and 2.87&#xa0;m in the central&#xa0;sector) shrinkages. This resulted in the prolonged inundation of low-lying areas and increased incidences of flash floods. Both sectors of the lake maintain limnetic and well-mixed conditions during the monsoon whereas during non-monsoon season, the central sector turns to polyhaline/mesohaline and oligohaline conditions with stratified, partially mixed, and well-mixed salinity stratifications unlike the south sector which perennially remain limnetic and well mixed. The observed shift in salinity regimes appears to promote hypertrophic conditions, biodiversity loss, and a sharp reduction in the black clam abundance of the south sector, which before the commissioning of Thannermukkom Barrage (TMB) was a major clam ground.</p>

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Impacts of faulty grey infrastructures on the bathymetry and salinity of Vembanad Lake, a tropical estuary along the south west coast of India

  • 期刊论文

  • 发表日期：

    2025年2月27日

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  • Vimal Kumar K. G.,
  • Sanjeevan V. N.

摘要

The fast degradation in bathymetry, floodwater retention capacity, and changes in salinity regimes of Vembanad—the largest wetland system in South India—and its impacts on the ecosystem services are assessed using high-resolution data sets on bathymetry and hydrography. Strengthening the outer banks of Kuttanad polders to promote paddy cultivation led to a sharp decline in its sediment (suspended) filtration potential, promoting heavy siltation and depth shrinkage of Vembanad Lake. With an area of 315 sq.km and an average depth of 8.5 m (south sector)/7.87 m (central sector), the lake had a retention capacity of 2617.5 MCM floodwaters in 1930 which was reduced to 384.7 MCM by 2020 (85.3% loss in retention capacity) due to area (162.5 sq.km) and depth (average 1.8 m in the south sector and 2.87 m in the central sector) shrinkages. This resulted in the prolonged inundation of low-lying areas and increased incidences of flash floods. Both sectors of the lake maintain limnetic and well-mixed conditions during the monsoon whereas during non-monsoon season, the central sector turns to polyhaline/mesohaline and oligohaline conditions with stratified, partially mixed, and well-mixed salinity stratifications unlike the south sector which perennially remain limnetic and well mixed. The observed shift in salinity regimes appears to promote hypertrophic conditions, biodiversity loss, and a sharp reduction in the black clam abundance of the south sector, which before the commissioning of Thannermukkom Barrage (TMB) was a major clam ground.