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High levels of P in the North Bosque River (NBR) have been attributed, in part, to confined dairy feeding operations (CAFOs) within the watershed. Through the Total Maximum Daily Load (TMDL) process the State of Texas has recommended a 50% reduction of P loading to the streams in the NBR watershed. One possible Best Management Process (BMP) is the export of manure P through turfgrass sod produced with composted dairy manure. Turfgrass from the NBR watershed would be harvested and shipped to developing urban and suburban areas in the Dallas-Fort Worth metroplex, including the Marys Creek watershed, which is a tributary of the Trinity River. The impact on water quality of manure P imported to the Mary's Creek watershed will be assessed using the Geographic Information Systems (GIS) based Soil and Water Assessment Tool (SWAT) model. Streamflow and sediment loading were successfully calibrated with the SWAT model by using GIS data of the physical and hydrologic properties of the Marys Creek watershed. The Root Mean Square Error (RMSE) was 0.58 and the Nash-Sutcliffe (NS) model fit efficiency was 0.67 when comparing calibrated predicted flow to measured streamflow. Sediment loading was simulated to within 2% of the annual estimated sediment loading at the outlet of Mary's Creek.