K G Vimal Kumar, V N Sanjeevan
Centre for Aquatic Resource Management and Conservation, Kerala University of Fisheries and Ocean Studies, Panangad, Kochi, 682506, Kerala, India.
Environ Monit Assess. 2025 Feb 27;197(3):336. doi: 10.1007/s10661-025-13773-5.
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.
利用高分辨率的水深测量和水文数据集，评估了印度南部最大的湿地系统——韦姆巴纳德湖的水深快速退化、洪水蓄留能力以及盐度状况变化及其对生态系统服务的影响。加强库坦纳德圩田的外堤以促进水稻种植，导致其沉积物（悬浮）过滤潜力急剧下降，促使韦姆巴纳德湖严重淤积和深度缩减。该湖面积为315平方公里，平均深度为8.5米（南部区域）/7.87米（中部区域），1930年其洪水蓄留能力为261750万立方米，到2020年由于面积（162.5平方公里）和深度（南部区域平均1.8米，中部区域平均2.87米）缩减，蓄留能力降至38470万立方米（蓄留能力损失85.3%）。这导致低洼地区长期被淹，山洪暴发的发生率增加。该湖的两个区域在季风期间保持湖沼学和充分混合的状态，而在非季风季节，中部区域变为多盐/中盐和寡盐状态，盐度分层为分层、部分混合和充分混合，与常年保持湖沼学和充分混合状态的南部区域不同。观察到的盐度状况变化似乎促进了富营养化状况、生物多样性丧失，以及南部区域黑蛤数量的急剧减少，在坦纳穆科姆水坝（TMB）建成之前，南部区域是主要的蛤类产地。
