[A-HW19] Hydrology & Water Environment

[AHW19-P06] Application of SWAT-MODFLOW Model in Srepok River Basin, Vietnam

*Sam Thao Truong¹, Hiroaki Somura¹ (1.Graduate School of Environmental and Life Science, Okayama University)

Keywords:Surface-groundwater interaction, SWAT-MODFLOW coupled model, Srepok River Basin

Srepok River Basin is considered a typical agricultural region with the highest coffee areas in Vietnam. To produce coffee with high productivity, water resources are believed one of the influencing key factors. In this area, water for coffee irrigation has been obtained from both surface water and groundwater. However, the knowledge gaps of surface-groundwater use have led to inappropriate management of water resources in this catchment and surrounding zones in recent years, especially in the dry season. Therefore, the SWAT-MODFLOW model was applied for assessing water resources. In the process, DEM, land-use, soil types, and meteorological information (precipitation, maximum/minimum temperature, relative humidity, or wind speed) were input to reproduce the streamflow in the Srepok River Basin. Then, by using ArcMap to divide HRUs of SWAT into DHRUs (Disaggregated Hydrologic Response Units) and link with grid cells in MODFLOW-NWT (a Newton-Raphson formulation of MODFLOW 2005), groundwater recharge was simulated. In the next step, streamflow and groundwater table were calibrated and validated, respectively. Finally, the performances of the integrated model were evaluated by statistical indices Nash-Sutcliffe efficiency (NSE), Coefficient of determination (R²), and percent bias (PBIAS). The results indicated that the coupled SWAT-MODFLOW model was capable of simulating surface-groundwater interaction in the Srepok River Basin. In the future, the model will be used for assessing the impact of coffee irrigation on water resources in this study area.