[A-HW22] Material transportation and cycling at the land-sea interface: from headwaters to the ocean

[AHW22-P11] Evaluating Long-Term Forest Growth Effects on Catchment Groundwater Recharge: Considering Canopy Dynamics

*Rendilicha Halake Guyo¹, Kunyang Wang², Mitsuyo Saito², Shin-ichi Onodera², Toshitsugu Moroizumi¹ (1.Okayama University, 2.Hiroshima University)

Keywords:SWAT model, Leaf Area Index, Evapotranspiration, Forested growth, Canopy dynamics

The demand for hydrological ecosystem services, including groundwater supply for drinking and carbon sequestration, from forested catchments has surged since the mid-19th century and persists due to ongoing environmental changes. This study addresses the critical need to evaluate the long-term impacts of tree growth on forest catchment groundwater conservation while considering canopy dynamics and climate change. We employ hydrological modeling to refine the representation of forest growth dynamics across various forest communities (including evergreen, deciduous, and mixed) within the SWAT model under long-term climate conditions. This is achieved through the integration of physically meaningful parameters derived from remote sensing products. Furthermore, to accurately portray natural forest growth ecosystems and slope dynamics within the catchment, we eliminate management operations in SWAT and adjust CN2 values for slopes. Extensive calibration and validation of the model outputs are conducted using MODIS-derived leaf area index (LAI), evapotranspiration (ET), and observed streamflow data. Results demonstrate that the improved model outperforms the original SWAT configuration, particularly in simulating LAI and ET, as well as CN2 variations on slopes, without necessitating further model modifications. The integration of MODIS-derived LAI, ET, and slope-dependent CN2 adjustments significantly enhances the estimation of hydrological fluxes within the catchment. These findings underscore the importance of accurately representing forest growth dynamics in natural settings and accounting for slope variations to effectively evaluate the long-term effects of tree growth on forest catchment groundwater conservation amid changing climate conditions.
Acknowledgments
This research was supported by JSPS Grant-in-Aid for Scientific Research (B) (No. 21H03650, PI: Mitsuyo Saito) and Fostering Joint International Research (A) (No. 20KK0262, PI: Mitsuyo Saito).