Development and evaluation of the Soil and Water Temperature Model (SWTM) for rural catchments

A physically-based energy balance model, the Soil and Water Temperature Model (SWTM), is developed in an effort to improve the soil temperature estimation for Korean rural watersheds or catchments, which are characterized by heterogeneous land-cover types and rugged topography and have many paddy fields retaining surface water during the growing season. The developed model is applied to a small rural catchment in South Korea where soil temperature is measured for two months, July to August 2008, at eight monitoring sites including forest, paddy field, dry field, and natural vegetation area. The degree of agreement between the simulated and observed soil temperature is quite good for the soil surface (RMSE 1.11-3.16 °C, R2 0.80-0.88), except for forests. Although some estimation errors resulting from data deficiency and model structure are observed, SWTM reasonably well simulates the spatial and temporal distribution of soil temperature at the catchment scale by considering the effects of topography, vegetation cover, and hydrological characteristics, especially the existence of surface water. SWTM is well suited for rural watersheds or catchments and expected to contribute to enhancing our understanding of watershed biogeochemical processes and managing the watershed environment.