Taylor Creek Impoundment was constructed on the western side of the upper St. Johns River basin as part of a plan for flood control and water regulation. The impoundment, which has a surface area of about 4,000 acres, was initially filled late in 1969. Water of relatively poor quality was observed in the impoundment during its first three years of its existence (1970-72).
The depth of the impoundment is sufficient to allow thermal stratification, and a thermocline usually develops at depths of 8 to 10 feet. During 1970-72 the hypolimnion remained anaerobic for more than half the year. The hypolimnion also accumulated high concentrations of phosphorus, ammonia-nitrogen, carbon dioxide, ferrous iron, hydrogen sulfide and other substances. The poor water quality is attributed to the decomposition of flooded vegetation, decomposition of soil organic matter, and heavy growths of phytoplankton and duckweed stimulated by an abundant supply of nutrients. Flushing of the impoundment and depletion of leachable nutrients and soil organic matter have led to an improvement in water quality since 1972.
During 1973 and 1974 the depth to the top of the anaerobic zone increased to more than 12 feet and by 1974 the period of anaerobiosis decreased to less than 2 months out of 12. Phosphorus concentration after the fall overturn decreased more than 50 percent between 1970 and 1974. The reduction in biochemical oxygen demand during this period suggests a decrease in primary productivity.
Water released from the impoundment during the period 1969-75 was similar in quality to nearby Wolf Creek and Jane Green Creek. Of 21 physical, organic, and inorganic constituents, only ammonia-nitrogen was significantly higher in releases from the impoundment than it was in the natural streams. Dissolved oxygen was higher in water released from the impoundment than in the natural streams and dissolved solids concentration were lower. Large releases from the impoundment may, under certain conditions, produce velocities great enough to resuspend bottom sediments several miles downstream at a point where Taylor Creek flows into Lake Poinsett.