There are approximately 3.3 million acres of freshwater wetland on the Texas coastal plain. They are the most rapidly decreasing coastal wetland type in Texas and are being lost most rapidly from the Galveston Bay and nearby estuarine watersheds (Moulton et al. 1997). This study evaluated the potential for freshwater isolated wetlands to positively affect water quality by documenting their role in the surface hydrology of southeast Texas estuarine watersheds.