Turbidity dynamics in Indian peninsular river mouths derived from Kd490 reveals key anthropogenic drivers

Sravanthi Nukapothula; Ali P Yunus; Sahil Kaushal; Chuqun Chen; A C Narayana

doi:10.1016/j.scitotenv.2023.165162

Turbidity dynamics in Indian peninsular river mouths derived from K_d490 reveals key anthropogenic drivers

Sci Total Environ. 2023 Oct 20:896:165162. doi: 10.1016/j.scitotenv.2023.165162. Epub 2023 Jun 27.

Authors

Sravanthi Nukapothula¹, Ali P Yunus², Sahil Kaushal³, Chuqun Chen⁴, A C Narayana⁵

Affiliations

¹ Centre for Earth, Ocean and Atmospheric Sciences, University of Hyderabad, Hyderabad, 500046, India; State Key Laboratory of Tropical Oceanography, Guangdong Key Lab of Ocean Remote Sensing, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China. Electronic address: sravantii73@gmail.com.
² Department of Earth and Environmental Sciences, Indian Institute of Science Education and Research Mohali, Punjab 140 306, India. Electronic address: yunusp@iisermohali.ac.in.
³ Department of Earth and Environmental Sciences, Indian Institute of Science Education and Research Mohali, Punjab 140 306, India.
⁴ State Key Laboratory of Tropical Oceanography, Guangdong Key Lab of Ocean Remote Sensing, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China.
⁵ Centre for Earth, Ocean and Atmospheric Sciences, University of Hyderabad, Hyderabad, 500046, India. Electronic address: acnes@uohyd.ac.in.

PMID: 37379919
DOI: 10.1016/j.scitotenv.2023.165162

Abstract

Large rivers, which act as natural integrators of surface processes, contribute massive volume of terrestrial materials to the coastal oceans. However, the accelerated climate warming and increasing anthropogenic activities recorded in recent years have been severely affecting the hydrologic and physical regimes of river systems. These changes have a direct impact on river discharge and runoff, some of which are occurred rapidly in the past two decades. Here, we present a quantitative analysis on the effects of changes in surface turbidity at coastal river mouths using diffuse attenuation coefficient at 490 nm (K_d490) as a proxy of turbidity for six major Indian peninsular rivers. The time series (2000-2022) trends of K_d490 obtained from Moderate Resolution Imaging Spectrometer (MODIS) images shows a significant decreasing trend in K_d values (p < 0.001) at the mouths of the Narmada, Tapti, Cauvery, Krishna, Godavari, and Mahanadi rivers. This is despite an increased rainfall trend observed for the six studied river basins which can likely intensifies the surface runoff and deliver more sediments, suggesting that other factors such as land use changes and increased number of dam constructions are primarily responsible for the decreased sediment load from rivers to coastal mouths.

Keywords: Anthropocene; Diffuse attenuation coefficient; Peninsular rivers of India; River discharge; Turbidity; Water transparency.