Cattle grazing, horse farms, citrus groves, and vegetable production (e.g., potatoes, winter vegetables) are the major farming activities.

Because of the extensive wetlands throughout the drainage basin, the St. Johns River is highly stained (brown) with humic color. Water in the river generally is quite hard—high in calcium, magnesium and alkalinity—as a result of inflows from groundwater and artesian springs connected to the calcareous Floridan Aquifer. Chloride concentrations also are high, even in the freshwater portions of the river, because of the influx of groundwater with high chloride levels. These characteristics provide challenges in treating the water for potable purposes. The river and its tributaries are rich in nutrients (nitrogen and phosphorus) as a result of runoff from agricultural and urban areas, as well as inflows of treated municipal wastewater. The nutrient levels promote luxurious growths of aquatic plants along the river edge and cause algal blooms in the major in-channel lakes, especially in the middle and lower St. Johns River.


This report is the final contribution of the NRC Committee tasked to review the WSIS. As an update of the Committee’s third report, which focused on results from the hydrology and hydrodynamics workgroup, Chapter 2 gives some final thoughts on the contributions of this workgroup, including the results of scenario analyses for the river. It also describes how the results from this workgroup were used by the seven environmental workgroups, including the issues of uncertainty and the sensitivity of the results. Chapter 3 critically evaluates the progress of the seven environmental workgroups. For each, it describes the conceptual model, summarizes the methods used by the workgroup, summarizes and analyzes the results, and makes conclusions and recommendations about the adequacy of the effort. Finally, Chapter 4 discusses a number of overarching themes, including the larger context surrounding the WSIS (such as sea level rise, dredging, water quality issues, population growth and land use change, and wastewater impacts). It makes general conclusions about the adequacy of the entire WSIS and provides some lessons to be learned for future studies on natural resource development versus impacts on environmental quality.

It should be noted that this report refers to District documents (particularly draft reports of the eight workgroups) that are likely to have been updated since the publication of this report.


NRC (National Research Council). 2009a. Review of the St. Johns River Water Supply Impact Study: Report 1. Washington, DC: The National Academies Press.

NRC. 2009b. Review of the St. Johns River Water Supply Impact Study: Report 2. Washington, DC: The National Academies Press.

NRC. 2010. Review of the St. Johns River Water Supply Impact Study: Report 3. Washington, DC: The National Academies Press.

SJRWMD (St. Johns River Water Management District). 2006. District Water Supply Plan, 2005. Technical Publication SJ2006-2. Palatka, FL: SJRWMD.

SJRWMD. 2009. Water Supply Assessment 2008. Technical Publication SJ2009. Palatka, FL: SJRWMD.

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