We can use the information we have about a place including its unique geological structure, hydrology, chemical and physical characteristics, and historical, current, or future land uses to map specific vulnerabilities for surface water and ground water resources. Surface water vulnerability Figure 1 shows overall surface water vulnerability in the St. Marks Basin, with the darkest areas being the most vulnerable. This is the Tallahassee Hills physiographic region, where the land surface is underlain by clayey sediments that retard the downward movement of water. Although there is an occasional surface connection to ground water through sinkholes, pollution mainly flows across the surface into the area s rivers and lakes. In contrast, the region that is least vulnerable to surface water pollution is the light area in the center, where soils are porous and water seeps rapidly into underground aquifers.
Additional vulnerability comes from both the intensity and type of local land uses.
In the city of St. Marks, for example, these land uses include an industrial complex, the Purdom power plant, refineries, and a fuel-storage area all on the banks of the St. Marks River. This kind of situation is common in the United States because, as discussed previously, water resources were long considered strictly utilitarian. Surface water vulnerability also increases because hazardous materials such as petroleum products are transported on the St. Marks River. Mark Brown, Ph.D., Center for Wetlands, Department of Environmental Engineering Sciences, University of Florida Ground water vulnerability Figure 2 shows groundwater vulnerability in the St. Marks Basin. The darkest area, the Woodville Karst Plain, shows the greatest vulnerability.