Jang et al. (2026) Integrating MODIS and SMAP data for spatially calibrated SWAT+ modeling in a forested watershed of South Korea

Identification

• Journal: Environmental Modelling & Software
• Year: 2026
• Date: 2026-09-08
• Authors: Wonjin Jang, Yong-Gu Lee, Yongwon Kim, Jeehun Chung, Seong‐Joon Kim
• DOI: 10.1016/j.envsoft.2026.107160

Research Groups

• Department of Hydro Science and Engineering Research, Korea Institute of Civil Engineering and Building Technology (KICT)
• Asia Infrastructure Research Center, Konkuk University
• Department of Civil, Environmental and Plant Engineering, Graduate School, Konkuk University
• Division of Civil and Environmental Engineering, College of Engineering, Konkuk University

Short Summary

This study integrates MODIS and SMAP data for spatially calibrated SWAT+ modeling in a forested watershed of South Korea. The results show that satellite-guided calibration improves the representation of hydrograph dynamics and reduces parameter equifinality.

Objective

• To develop a spatially explicit, sequential multi-variable calibration strategy for SWAT+, designed to reflect the process hierarchy linking vegetation phenology (LAI), evapotranspiration (ET), and soil moisture (SM).
• To evaluate the degree to which spatial parameter calibration improves watershed water balance and hydrologic realism.

Study Configuration

• Spatial Scale: Landscape unit (LSU) scale, with 13 LSUs in the Yongdam Dam watershed.
• Temporal Scale: Daily to monthly time steps for SWAT+ simulations, with MODIS and SMAP data used at 8-day and 3-hourly intervals, respectively.

Methodology and Data

• Models used: Soil and Water Assessment Tool (SWAT+) model, with MODIS and SMAP data integrated for calibration.
• Data sources:
  • MOD15A2H.061 product provides 8-day composite global fields of LAI from Terra-MODIS at 500 m resolution.
  • MOD16A2GF.061 product provides 8-day composites of ET and latent heat flux (LE) at 500 m, derived from the Penman-Monteith based algorithm.
  • SPL4SMGP.007 SMAP L4 surface and root zone soil moisture product provides 9 km, 3-hourly surface soil moisture.

Main Results

• The SWAT+ LAI simulation showed a strong correlation with MODIS LAI data (R2 > 0.94).
• Evapotranspiration calibration resulted in average R2 values ranging from 0.69 to 0.84 and average RMSE of 4.70 mm/8-day.
• Soil moisture calibration required substantial parameter adjustments, with AWC increased by 75% and soil_k decreased by 75% across all LSUs.

Contributions

• This study demonstrates a generalizable satellite-guided calibration approach for long-term SWAT+ simulations.
• The results show that spatial parameter calibration improves watershed water balance and hydrologic realism.

Funding

• Not specified in the provided text.

Citation

@article{Jang2026Integrating,
  author = {Jang, Wonjin and Lee, Yong-Gu and Kim, Yongwon and Chung, Jeehun and Kim, Seong‐Joon},
  title = {Integrating MODIS and SMAP data for spatially calibrated SWAT+ modeling in a forested watershed of South Korea},
  journal = {Environmental Modelling & Software},
  year = {2026},
  doi = {10.1016/j.envsoft.2026.107160},
  url = {https://doi.org/10.1016/j.envsoft.2026.107160}
}