Submitted as: model description paper 15 Mar 2021

Submitted as: model description paper | 15 Mar 2021

Review status: this preprint is currently under review for the journal GMD.

Development of a coupled simulation framework representing the lake and river continuum of mass and energy (T-CHOIR v1.0)

Daisuke Tokuda1, Hyungjun Kim1, Dai Yamazaki1, and Taikan Oki2,3 Daisuke Tokuda et al.
  • 1Institute of Industrial Science, University of Tokyo, Tokyo, Japan
  • 2Graduate School of Engineering, The University of Tokyo, Tokyo, Japan
  • 3United Nations University, Tokyo, Japan

Abstract. Terrestrial surface water temperature is a key variable affecting water quality and energy balance, and thermodynamics and fluid dynamics are tightly coupled in fluvial and lacustrine systems. Streamflow generally plays a role in the horizontal redistribution of heat, and thermal exchange in lakes predominantly occurs in a vertical direction. However, numerical models simulate the water temperature for uncoupled rivers and lakes, and the linkages between them on a global scale remain unclear. In this study, we proposed an integrated modeling framework: Tightly Coupled framework for Hydrology of Open water Interactions in River–lake network (T-CHOIR). The objective is to simulate terrestrial fluvial and thermodynamics as a continuum of mass and energy in solid and liquid phases redistributed among rivers and lakes. T-CHOIR uses high-resolution geographical information harmonized over fluvial and lacustrine networks. The results have been validated through comparison with in-situ observations and satellite-based data products, and the model sensitivity has been tested with multiple meteorological forcing datasets. It was observed that the coupled mode outperformed the river-only mode in terms of discharge and temperature in downstream of lakes; it was also observed that seasonal and interannual variation in lake water levels and temperature are also more reliable in the coupled mode. The inclusion of lakes in the coupled model resulted in an increase in river temperatures during winter in mid-latitudes and a decrease in temperatures during summer in high latitudes, which reflects the role of lakes as a form of large heat storage. The river–lake coupling framework presented herein provides a basis for further elucidating the role of terrestrial surface water in in Earth’s energy cycle.

Daisuke Tokuda et al.

Status: open (until 10 May 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gmd-2021-75', Shuqi Lin, 13 Apr 2021 reply
  • RC2: 'Comment on gmd-2021-75', Anonymous Referee #2, 20 Apr 2021 reply

Daisuke Tokuda et al.

Model code and software

T-CHOIR: Tightly Coupled framework for Hydrology of Open water Interactions in River–lake network Daisuke Tokuda, Hyungjun Kim, Dai Yamazaki, and Taikan Oki

Daisuke Tokuda et al.


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Short summary
We developed the T-CHOIR, a hydrologic simulation framework, to solve fluvial- and thermo- dynamics of river-lake continuum. This provides an algorithm for upscaling high-resolution topography as well, which enables the representation of those interactions at the global scale. Validation against in-situ and satellite observations shows that the coupled mode outperforms river or lake only modes. T-CHOIR will contribute to elucidate the role of surface hydrology in Earth’s energy and water cycle.