Implications for the Missing South Asian Carbon Sink: Hydrologic Coupling of Water and Carbon Balances in a Tropical Catchment

Senarathne SL, van Geldern R, Chandrajith R, Chiogna G, Barth J (2025)

Publication Language: English

Publication Type: Journal article

Publication year: 2025

Journal

Journal of Geophysical Research: Biogeosciences American Geophysical Union

Book Volume: 130

Article Number: e2025JG008839

Journal Issue: 7

DOI: 10.1029/2025JG008839

Abstract

This study applied stable water isotopes (δ18OH2O and δ2HH2O) and remote sensing techniques to predict basin-wide CO2 uptake in the tropical Deduru Oya River Basin (DOB) in Sri Lanka. It used the fact that water and carbon cycles are linked by transpiration. Between November 2022 and October 2023, the DOB lost 2,563 million m3 of water by evapotranspiration (ET). This number corresponds to 65.8% of the 3,895 million m3 of incoming precipitation. Based on the δ18OH2O in a revised Craig–Gordon model and normalized difference vegetation index (NDVI), our data showed that ET could be separated into its subcomponents evaporation (E), transpiration (T), and interception (I) with 10.4%, 53.9%, and 1.5% of the annual precipitation, respectively. After translation to carbon uptake via the water use efficiency (WUE), the DOB showed a net primary productivity (NPP) of 1,130 g C m−2 that corresponded to 2,808 × 109 g C for the entire basin. After subsequent subtraction of basin-wide soil respiration (1,737 × 109 g C) and surface water degassing (101 × 109 g C) back to the atmosphere, our study yielded a net ecosystem production (NEP) of 979 ± 313 × 109 g C for the entire basin. These result indicate that the DOB is a carbon sink. Our study is the first to present this technique together with error propagation and with CO2 evasions from surface waters.

Authors with CRIS profile

Sachintha Lakshan Senarathne Lehrstuhl für Angewandte Geologie Robert van Geldern Lehrstuhl für Angewandte Geologie Rohana Chandrajith Lehrstuhl für Angewandte Geologie Gabriele Chiogna Professur für Angewandte Geologie und Modellierung von Umweltsystemen Johannes Barth Lehrstuhl für Angewandte Geologie

How to cite

APA:

Senarathne, S.L., van Geldern, R., Chandrajith, R., Chiogna, G., & Barth, J. (2025). Implications for the Missing South Asian Carbon Sink: Hydrologic Coupling of Water and Carbon Balances in a Tropical Catchment. Journal of Geophysical Research: Biogeosciences, 130(7). https://doi.org/10.1029/2025JG008839

MLA:

Senarathne, Sachintha Lakshan, et al. "Implications for the Missing South Asian Carbon Sink: Hydrologic Coupling of Water and Carbon Balances in a Tropical Catchment." Journal of Geophysical Research: Biogeosciences 130.7 (2025).

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