2.7.9. Doctors Lake

2.7.9.1. About Doctors Lake

Figure 2.38
Figure 2.36 The Doctors Lake Tributary (WBID 2389 and 2410).
  • West of the St. Johns River in Clay County
  • Primary Land Use: Forested
  • Current TMDL reports: Nutrient – 2389 (draft), DO/Nutrient – 2410 (draft), Silver – 2389/2410
  • Verified Impaired 2016 (final): Nutrients (Chlorophyll-a 2389 med), Nutrients (Total P 2389 med)
  • WBID Area: 8.4 sq. mi.
  • Beneficial Use: Class III F (Recreational – Freshwater)

2.7.9.2. Data sources

Result data was downloaded from the FL STORET and WIN websites (DEP 2010f; DEP 2018h) and filtered based on the stations (DEP 2010g) in Doctors Lake WBIDs 2389 and 2410 (DEP 2014c) shown above. The filtered dataset was used to generate Table 2.10, with freshwater stream WQC’s reported. These should be regarded as guidelines only because Swimming Pen creek (2410) is accessed as a stream, Doctors Lake (2389) is accessed as a lake and has different WQC’s.

2.7.9.3. Discussion

Water quality data for Doctors Lake are shown in Table 2.10. The average total phosphorus concentration has hovered around the criterion value for colored lakes (0.05 mg/L) the past three years.  Average dissolved oxygen levels are well above the SSAC. Doctors Lake has been identified as being impaired for nutrients (chlorophyll-a and total phosphorus) (DEP 2016j), and the final TMDL report to address this has been published (Magley 2009e). Recent water samples continue to show elevated phosphorus concentrations.

Elevated maximum arsenic, cadmium, copper, nickel, silver, and zinc concentrations were previously measured in Doctors Lake, and as a result, EPA has published a Silver TMDL (EPA 2010a). Doctors Lake is largely used for recreational activities such as boating, fishing, and waterskiing. These activities could account for some of the copper, nickel, and zinc contamination; however, the source of the other contamination is not clear. Recent data show that concentrations of these contaminants have remained roughly steady over the past three years.

No recent measurements were available in WIN or STORET from 2016 to 2018 for the following parameters:

  • Fecal Coliform

Historical water quality data for Doctors Lake are available in previous versions of the River Report. 

Table 2.10 Water quality data for Doctors Lake.

 Water QualityAverage and Number of Samples º
ParameterCriteria (FW)201620172018
Dissolved Oxygen (mg/L)≥34% sat. (≥3.0)8.34
(0 of 27 samples)
7.90
(1 of 20 samples)
6.23
(4 of 28 samples)
Total Nitrogen (mg/L)<1.541.00
(0 of 7 samples)
Not availableNot available
Total Phosphorus (mg/L)<0.050.06
(7 of 16 samples)
0.07
(7 of 14 samples)
0.10
(15 of 16 samples)
Chlorophyll-a (µg/L)<2023.59
(4 of 9 samples)
117.02
(5 of 8 samples)
14.63
(3 of 8 samples)
Arsenic (µg/L)≤501.56
(0 of 9 samples)
2.40
(0 of 6 samples)
2.75
(0 of 8 samples)
Cadmium (µg/L)≤0.30.00
(0 of 9 samples)
0.06
(0 of 6 samples)
0.03
(0 of 8 samples)
Copper (µg/L)≤9.31.00
(0 of 9 samples)
0.95
(0 of 6 samples)
2.75
(0 of 8 samples)
Lead (µg/L)≤3.2Not availableNot available0.54
(0 of 8 samples)
Nickel (µg/L)≤520.38
(0 of 9 samples)
0.22
(0 of 6 samples)
0.56
(0 of 8 samples)
Silver (µg/L)≤0.070.00
(0 of 9 samples)
0.00
(0 of 6 samples)
0.06
(1 of 8 samples)
Zinc (µg/L)≤1201.39
(0 of 9 samples)
1.29
(0 of 6 samples)
2.50
(0 of 8 samples)
Turbidity (NTU)<29Not availableNot available4.38
(0 of 7 samples)
Note: Hardness-dependent freshwater criteria for cadmium, copper, lead, nickel, and zinc were generated based on a hardness concentration of 100 mg/L.
° = Number of samples below Water Quality Criteria for Dissolved Oxygen; Number of samples above Water Quality Criteria for all other parameters.
FW = freshwater; SW = saltwater (marine). Values denoted with (*) indicate a proposed criterion, which has not yet been adopted.
Values denoted with (‡) are reference values based on EPA criteria (EPA 2010b), but the water body is not regulated by this standard.