Abstract
The United Nation’s Sustainable Development Goal Life Below Water (SDG-14) aims to “conserve and sustainably use the oceans, seas, and marine resources for sustainable development”. Within SDG-14, targets 14.1 and 14.2 deal with marine pollution and the adverse impacts of human activities on aquatic systems. Here, we present a remote-sensing-based analysis of short-term changes in the Vembanad-Kol wetland system in the southwest of India. The region has experienced high levels of anthropogenic pressures, including from agriculture, industry, and tourism, leading to adverse ecological and socioeconomic impacts with consequences not only for achieving the targets set out in SDG-14, but also those related to water quality (SDG-6) and health (SDG-3). To move towards the sustainable management of coastal and aquatic ecosystems such as Lake Vembanad, it is important to understand how both natural and anthropogenic processes affect water quality. In 2020, a unique opportunity arose to study water quality in Lake Vembanad during a period when anthropogenic pressures were reduced due to a nationwide lockdown in response to the global pandemic caused by SARS-CoV-2 (25 March–31 May 2020). Using Sentinel-2 and Landsat-8 multi-spectral remote sensing and in situ observations to analyse changes in five different water quality indicators, we show that water quality improved in large areas of Lake Vembanad during the lockdown in 2020, especially in the more central and southern regions, as evidenced by a decrease in total suspended matter, turbidity, and the absorption by coloured dissolved organic matter, all leading to clearer waters as indicated by the Forel-Ule classification of water colour. Further analysis of longer term trends (2013–2020) showed that water quality has been improving over time in the more northern regions of Lake Vembanad independent of the lockdown. The improvement in water quality during the lockdown in April–May 2020 illustrates the importance of addressing anthropogenic activities for the sustainable management of coastal ecosystems and water resources.
Highlights
Dissolved organic matter at 440nm (aCDOM(440)); (D) turbidity; and (E) the Forel-Ule classification ofcolour water class) during the lockdown after March 25 compared with values one month before the lockdown for 2020, and for the same class) during the lockdown after March 25 compared with values one month before the lockdown for 2020, and for the period in 2013–2019
We showed that water quality improved in large areas of Lake Vembanad during April 2020 as evidenced by a decrease in total suspended matter (TSM), absorption by coloured dissolved organic matter (aCDOM), and turbidity, all leading to clearer waters as indicated by the FU classification of water colour
We showed that a coordinated response in reducing anthropogenic activities that may violate the regulations in place can improve water quality, with the potential to sustain and/or restore the ecological values of Lake Vembanad in the future [7,32,52]
Summary
Despite considerable efforts to protect vulnerable marine, coastal, and freshwater ecosystems, anthropogenic activities remain one of the main causes of poor water quality in Remote Sens. Stretching approximately 100 km and covering over 241 km , Lake Vembanad is the second largest lake in India This semi-enclosed lake supports an exceptionally large biodiversity and is rich in water birds, fish, and aquatic plants [5,6,7]. Despite its protected status and its importance to the livelihood of local communities, the Lake Vembanad ecosystem is under pressure from domestic waste and sewage, industrial pollution including heavy metal contaminations, eutrophication, and aquatic weed infestation [6,9,10,11,12]. Over 5000 instances of “land modifications” have taken place in the past with the majority deemed to violate the Coastal Regulation Zone guidelines of the Indian Environment Protection
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