As part of the spring inventory process, field water quality measurements were made during site visits where possible. Measurements were made for water temperature (degrees C), dissolved oxygen (mg/L), pH (standard units), and specific conductivity (umhos/cm). The results of these measurements are presented in Table 2.
Temperature can be highly variable in surface water dependent on atmospheric conditions. Ground water temperatures tend to be much more stable. For instance, long-term water temperature readings at Wakulla Springs — a first magnitude Floridan Aquifer spring in Wakulla County—reveal that the temperature typically has a median value of 20.79 degrees C (n=4120, mean=20.77, stdev=0.11). The median temperature of the Chipola River springs, 20.22 degrees C (n=49, mean= 20.07, stdev=0.81) compares well with this typical Floridan Aquifer value.
A surface water body with a dissolved oxygen (DO) value of less than 5.0 mg/L is considered impaired. The longer ground water remains in the aquifer, however, the lower the DO concentration becomes due to oxidation reactions with the matrix material. DO values in the Floridan Aquifer in this area typically have a median value of 0.16 (n=30, mean=1.76, stdev=2.39). The median DO value for the Chipola River Springs is 5.58 mg/L (n=48, mean=5.36, stdev=1.62). The higher DO values measured for the springs indicate a much shorter average residence time in the aquifer for the springs discharge compared to ground water in the Floridan Aquifer wells.
The spring pH values indicate that the water is well buffered. This is typical of water that has remained in the Floridan Aquifer for any length of time. The dissolution of limestone by acidic rain water raises the pH of the water and creates the characteristic karst topography of the Dougherty Karst Plain. Typical Floridan Aquifer pH values have a median of 7.79 standard units (n=30, mean=7.76, stdev=0.68). The median value of the Chipola River Springs is 7.46 standard units (n=49, mean=7.46, stdev=0.26).
Specific conductivity is a measure of the ion content of water. Rain water and surface water not influenced by ground water input usually have a specific conductivity value of less than 50 umhos/cm. The median specific conductivity value for Floridan Aquifer wells recently sampled in this area is 256 umhos/cm (n=30, mean=333, stdev=223). The median specific conductivity of the Chipola River Springs is 246umhos/cm (n=49, mean=249, stdev=59).
The high DO values and lower pH and specific conductivity values are probably the result of an influx of lower residence time, less mineralized and more acidic ground water into the Floridan Aquifer before it discharges from the springs. Because of this high local recharge and the significant surface water – ground water interaction within this highly karstic environment, the springs along the Chipola River are particularly vulnerable to proximate land use activities. There is no doubt, however, that these springs discharge Floridan Aquifer water.