2.7 Tributaries

2.7.1. About the Tributaries

Water quality data were examined in detail for 29 tributaries in the LSJRB. Their selection was based upon several factors. First, the basin was divided into the 11 Planning Units that were initially established by the SJRWMD and subsequently adopted by DEP (DEP 2002). These Planning Units include Crescent Lake, Etonia Creek, Black Creek, Deep Creek, Sixmile Creek, Julington Creek, the Ortega River, the Trout River, the Intracoastal Waterway, the north mainstem, and the south mainstem. Each Planning Unit is made up of several waterbodies (parts of the river system) referred to by their Waterbody Identification (WBID). Then, each Planning Unit was reviewed, in order to choose WBIDs for analysis. A WBID was selected for analysis if it had enough sampling sites at which data had been collected. Often, if a WBID was on the verified impaired list in 2004, 2009, or 2014 (DEP 2014g), it was selected for analysis. Some unimpaired WBIDs were chosen because they are historically important or used frequently for recreation.

For each of these 29 tributaries, data were extracted (by characteristic) from Florida STORET and organized by WBID. The datasets were filtered to remove data that was deemed to be “invalid” for one or more of the following reasons (values in quotes are written as they are found in Florida STORET data fields).

  • Data identified as “LEGACY STORET” (data is reported from 1997 onward).
  • Data reported as “Present < PQL,” where no Practical Quantitation Limit (PQL) was listed.
  • Data reported as “Non-detect,” where no Minimum Detection Level (MDL) was listed.
  • Data with a matrix of “Ground Water,” “Surface Water Sediment,” and ”Unknown.”

In previous reports, all “Non-detect” data had been removed. While seemingly a logical approach, the effect tends to bias the quartiles calculated in the data analysis on the high side. As a result, “Non-detect” data (and data reported as zero concentration) has been included in the data analysis here with a value MDL/2 (see Helsel 2005). In a similar manner, values listed as “Present < PQL”, were included as (PQL+MDL)/2 if no “Actual value” was reported in the “Comments” field. If an “Actual value” was reported in the “Comments” field, it was used instead.

In the ‘About’ sections for each of the 29 tributaries below, information/data was taken from the TMDL documents about each tributary respectively, the Florida DEP comprehensive verified impaired list (DEP 2014g), and the final verified list (DEP 2016j) and delist list (DEP 2016h) from the recent Group 2 basins Cycle 3 assessment (DEP 2016i).

In the water quality data tables below, dissolved oxygen (DO) water quality criteria (WQC) where either based on Site Specific Alternate Criteria (SSAC) (DEP 2014c) for marine portions of the river or the new freshwater DO criteria based on DO saturation in water (DOsat) (DEP 2013n). As both of these criteria definitions are calculation based, the WQCs indicated in the tables should be considered nominal values.

Finally, freshwater WQC’s for metals were based off of 100 mg CaCO3/L, the estimated hardness of the freshwater part of the LSJR (see Section 5.2.1 for more information).

Figure 2.23
Figure 2.23 Tributaries of the Lower St. Johns River Basin.