2.7.9. Doctors Lake

2.7.9.1. About Doctors Lake

Figure 2.38
Figure 2.39 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 website (DEP 2010e) and filtered based on the stations (DEP 2010f) in Doctors Lake WBIDs 2389 and 2410 (DEP 2014c) shown above. The filtered dataset was used to generate Table 2.8, 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 2.8. Average chlorophyll-a concentrations far exceeded the WQC, and this has worsened over the past three years.  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. Thus, 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).

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 STORET from 2015 to 2017 for the following parameters:

  • Nitrate-nitrite nitrogen
  • Lead
  • Fecal Coliform
  • Turbidity

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

Table 2.8 Water quality data for Doctors Lake (2015-2017).

 Water QualityAverage and Number of Samples º
ParameterCriteria201520162017
Dissolved Oxygen (mg/L)≥34% sat.
(≥3.0)
6.87
(3 of 36 samples)
8.34
(0 of 27 samples)
7.90
(1 of 20 samples)
Total Phosphorus (mg/L)<0.050.07
(12 of 20 samples)
0.06
(7 of 16 samples)
0.07
(7 of 14 samples)
Chlorophyll-a (µg/L)<2027.48
(5 of 12 samples)
23.59
(4 of 9 samples)
117.02
(5 of 8 samples)
Arsenic (µg/L)≤501.75
(0 of 11 samples)
1.56
(0 of 9 samples)
2.40
(0 of 6 samples)
Cadmium (µg/L)≤0.30.00
(0 of 11 samples)
0.00
(0 of 9 samples)
0.06
(0 of 6 samples)
Copper (µg/L)≤9.31.01
(0 of 11 samples)
1.00
(0 of 9 samples)
0.95
(0 of 6 samples)
Nickel (µg/L)≤520.25
(0 of 11 samples)
0.38
(0 of 9 samples)
0.22
(0 of 6 samples)
Silver (µg/L)≤0.070.04
(0 of 11 samples)
0.00
(0 of 9 samples)
0.00
(0 of 6 samples)
Zinc (µg/L)≤1202.33
(0 of 11 samples)
1.39
(0 of 9 samples)
1.29
(0 of 6 samples)
Note: Hardness-dependent freshwater criteria for cadmium, copper, lead, nickel, and zinc were generated based on a hardness concentration of 100 mg/L.
º = Number of samples below WQC for Dissolved Oxygen, Number of samples above WQC 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.
§ = No water quality criterion has been established for Nitrate-Nitrite nitrogen. No Total Nitrogen data were available in STORET for 2015-2017.