The objective of this study is to characterize the effects of existing structures and practices on the circulation and salinity patterns of the CCBNEP study area which includes three of the seven major estuary systems of the Texas Gulf Coast. These estuaries, the Aransas, Corpus Christi, and Upper Laguna Madre are biogeographically distinct and increase in salinity from north to south. The Laguna Madre in unusual in being only one of three hypersaline lagoon systems in the world. The study area is bounded on its eastern edge by a series of barrier islands, including the world's longest--Padre Island.