Technical Abstract: The Soil and Water Assessment Tool (SWAT), MODFLOW, and Energy Balance based Evapotranspiration (EB_ET) models are extensively used to estimate different components of the hydrological cycle. Surface and subsurface hydrological processes are modeled in SWAT but limited to the extent of shallow aquifers while MODFLOW concentrate on groundwater movement. Therefore, neither SWAT nor MODFLOW can independently simulate the full extent of the hydrological cycle at the watershed scale. Further, spatially variable recharge inputs to MODFLOW are normally assumed constant and estimated as a percentage of rainfall, which is does not realistically represent this spatial and temporally variable and management responsive process. In this study, a framework coupling SWAT (v. 477) and Newton Formulation for MODFLOW-2005 (MODFLOW-NWT) was developed to allow interaction of fluxes between SWAT hydrological units (HRUs) and MODFLOW-NWT grids at user defined time steps. Also, new tools were developed using DELPHI programming language in Windows environment to assist users to develop and setup the coupled models. The integrated SWAT-MODFLOW-NWT model system was evaluated using the Fort Cobb experimental watershed datasets for the period 2005-2010. Measured groundwater levels from the underlying Rush Spring aquifer and flow data at daily time-step from four USGS gauges located within the watershed were used for this purpose. Calibration and validation results from this study will be presented and discussed. The next phase will involve incorporating an EB_ET model that can provide improved evapotranspiration (ET) estimates to calibrate or substitute for ET in SWAT model.