Coupled modelling and sampling approaches to assess the impacts of human water management on land-sea carbon transfer

Shaoqiang Ni; Xiao Huang; Weixiu Gan; Conrad Zorn; Yuchen Xiao; Guorui Huang; Chaoqing Yu; Jifu Cao; Jie Zhang; Zhao Feng; Le Yu; Guanghui Lin; Hanna Silvennoinen

doi:10.1016/j.scitotenv.2019.134735

Coupled modelling and sampling approaches to assess the impacts of human water management on land-sea carbon transfer

Sci Total Environ. 2020 Jan 20:701:134735. doi: 10.1016/j.scitotenv.2019.134735. Epub 2019 Oct 22.

Authors

Shaoqiang Ni¹, Xiao Huang², Weixiu Gan¹, Conrad Zorn³, Yuchen Xiao¹, Guorui Huang¹, Chaoqing Yu⁴, Jifu Cao⁵, Jie Zhang⁶, Zhao Feng¹, Le Yu¹, Guanghui Lin¹, Hanna Silvennoinen⁷

Affiliations

¹ Department of Earth System Science, Ministry of Education Key Laboratory for Earth System Modeling, Tsinghua University, Beijing 100084, China.
² Norwegian Institute of Bioeconomy Research, Saerheim, 4353, Norway. Electronic address: xiao.huang@nibio.no.
³ Environmental Change Institute, University of Oxford, Oxford OX1 3QY, UK.
⁴ Department of Earth System Science, Ministry of Education Key Laboratory for Earth System Modeling, Tsinghua University, Beijing 100084, China; AI for Earth Laboratory, Cross-strait Tsinghua Research Institute, Xiamen 361000, China. Electronic address: chaoqingyu@yahoo.com.
⁵ Zhanjiang Hydrology Branch of Guangzhou Hydrology Bureau, Zhanjiang 524000, China.
⁶ Key Laboratory for Geo-Environmental Monitoring of Coastal Zone (GEMCO) of the National Administration of Surveying, Mapping and GeoInformation, Shenzhen University, Shenzhen 518060, China.
⁷ Norwegian Institute of Bioeconomy Research, Ås 1430, Norway.

PMID: 31704400
DOI: 10.1016/j.scitotenv.2019.134735

Abstract

Land-sea riverine carbon transfer (LSRCT) is one of the key processes in the global carbon cycle. Although natural factors (e.g. climate, soil) influence LSRCT, human water management strategies have also been identified as a critical component. However, few systematic approaches quantifying the contribution of coupled natural and anthropogenic factors on LSRCT have been published. This study presents an integrated framework coupling hydrological modeling, field sampling and stable isotope analysis for the quantitative assessment of the impact of human water management practices (e.g. irrigation, dam construction) on LSRCT under different hydrological conditions. By applying this approach to the case study of the Nandu River, China, we find that carbon (C) concentrations originating from different land-uses (e.g. forest, cropland) are relatively stable and outlet C variations are mainly dominated by controlled runoff volumes rather than by input C concentrations. These results indicate that human water management practices are responsible for a reduction of ∼60% of riverine C at seasonal timescales, with an even greater reduction during drought conditions. Annual C discharges have been significantly reduced (e.g. 77 ± 5% in 2015 and 39 ± 11% in 2016) due to changes in human water extraction coupled with climate variation. In addition, isotope analysis also shows that C fluxes influenced by human activities (e.g. agriculture, aquaculture) could contribute the dominant particulate organic carbon under typical climatic conditions, as well as drought conditions. This research demonstrates the substantial effect that human water management practices have on the seasonal and annual fluxes of LSRCT, especially in such small basins. This work also shows the applicability of this integrated approach, using multiple tools to quantify the contribution of coupled anthropogenic and natural factors on LSRCT, and the general framework is believed to be feasible with limited modifications for larger basins in future research.

Keywords: Field sampling; Human water management; Hydrological modeling; Land-sea carbon transfer; Stable isotope analysis.