Application of canal locations within grid cells to the study of surface water-groundwater interaction

Within St. Lucie County, Florida, a network of canals has been cut to provide flood protection, drainage, and irrigation. Many of these canals maintain a permanent to semi-permanent hydraulic connection with the surficial aquifer. MODFLOW code was used to simulate St. Lucie County groundwater levels. One of stresses that contributed to the solution of the groundwater levels, was the volume of water that flowed into or out of the aquifer through the canal system. In MODFLOW, the flow calculation between a canal and the aquifer is independent of the canal's location within the grid cell. The flow calculation was modified to incorporate canal location. Simulation results showed 34 percent of the model area realized groundwater levels that were plus or minus two-tenths to one-half foot when compared to the original levels. These results can be significant for model applications such as wetland protection and salt water intrusion.