Spatial Displays of South Florida Water Quality Data


Google Earth Layer:



File Updated:†† March 31, 2017


William W. Walker, Jr., Ph.D., Environmental Engineer


prepared for US Department of the Interior


This Google Earth layer displays grab-sample water quality data collected in South Florida between Water Years 2008 and 2017 (May 2007 - April 2017).Water Year 2017 values are currently updated thru January 2017.The data have been compiled from South Florida Water Management District's DBHYDRO database and research programs.†† Sampling frequencies are generally monthly for marsh sites and biweekly for canal sites.†† The displays are intended to depict spatial variations in water quality, not to reflect compliance with state or federal standards.

For purposes of displaying the data, monitoring sites are broadly categorized as marsh sites or canal sites. Canal sites include data from canals, structures, and pump stations.Marsh sites include data from the Everglades Protection Area, Big Cypress, Lake Okeechobee, and Florida Bay.

Water quality data are paired with daily flow data at each site.Flows are directly measured at canal sites or taken from the nearest upstream or downstream location.†† While direct measurements of flow at marsh sites are generally not available, pairing marsh water quality data with corresponding basin outflows provides perspectives on temporal variations in water quality related to flow.The combined outflows from Lake Okeechobee are paired with Lake sites.The combined outflows from WCA-1, WCA-2A, or WCA-3A are paired with marsh sites in the Water Conservation Areas. The combined inflows across different sections of the L29 canal (S12A to S334) are used for ENP marsh sites in Shark River Slough.A constant flow is assumed at Florida Bay sites.†† Flows discharged from structures or pump stations immediately upstream are used for marsh transects.

Water variables include nutrients (Total P, Total N, Total N/P Ratio, Potassium, and Potassium/Total Phosphorus Ratio), inorganic chemistry (Chlorides, Sulfate, Calcium), and field data (Temperature, pH, Specific Conductance, Dissolved Oxygen Percent Saturation, Dissolved Oxygen as a percent of DO-SSAC), and Alkaline Phosphatase.


DO-SSAC is Florida DEPís Site-Specific Alternative Criterion for dissolved oxygen levels at marsh sites in the Everglades Protection Area.†† The criterion adjusts for the impacts of variations in water temperature and time of sample collection on DO levels.The ratio is computed based upon paired sample values for DO concentration, water temperature, and time-of-day, then averaged across samples within each year.†† This is slightly different from the FDEP compliance test, which averages the DO and DOSSAC separately within each year before determining compliance.†† See Florida's water quality standards.

Water quality data for the 10-year period are summarized as follows:


       Geometric Means (GMs).The long-term geometric mean is computed as the arithmetic mean of yearly geometric means, as per Florida DEPís 4-Part test for tracking marsh levels relative to the 10-ppb Phosphorus Criterion.†† While FDEP screens the data for purposes of measuring compliance, all grab-sample data collected at marsh sites are used here, regardless of flow, the number of samples per year, or the distribution of samples between wet and dry season.†† At canal sites, data collected on days without flow are excluded.†† Geometric means are computed only for variables that are typically log-normally distributed (Total Phosphorus, Total Nitrogen, Total N/P ratio, Total K/P ratio).Arithmetic means are used for the other water quality variables.


       Arithmetic Means (AMs).The long-term arithmetic mean is computed as the arithmetic mean of the yearly arithmetic means using all of the data at marsh sites and data collected on dates with positive flow at canal sites.

       Flow-Weighted-Means (FWMs).†† The long-term flow-weighted mean is computed directly from the paired daily flow and grab-sample concentration data without summarizing by year.While flow-weighting is not typically done for marsh data, the FWMs are more heavily influenced by high flow conditions when downstream transport is important.†† Since a constant flow is assumed at Florida Bay sites, the computed AMs and FWMs are equal.


The Google Earth interface is displayed below:

Folders summarize data for specific water quality variables.†† Folders with average water depths on sampling dates, average flows on sampling dates, and SFWMD watershed boundaries (downloaded from DBHYDRO) are included.

Sub-folders display arithmetic means, geometric means, flow-weighted means, total number of samples, number of years with data, and site labels.Double clicking displays the entire network of sites. Single clicking maintains the current imagery and view.To focus on a particular region, double-click on a sub-folder in the "Basin Views" folder.††

Map symbols are labeled with the site GM or AM (balloon) or FWM (balloon with dot in center) values. Blue symbols represent marsh sites.Orange symbols represent canal sites.Click on a balloon to see station information and dataset values.

The height of a balloon tail above ground is proportional to (Min (Conc, Cmax) - Cmin), where Cmax is the maximum value for scaling and Cmin is the minimum value for scaling.†† The parameter values are listed in the dataset (click on a balloon).Cmin is set to 0 for all parameters except for pH (6 ) and temperature (18 deg-C).Cmax is set at a value close to or above the maximum value in the dataset.Capping the maximum balloon height at Cmax reduces the impact of sites with extremely high values and provides higher resolution of values in the low concentration range. The actual AM, GM, or FWM values are displayed as text on the map.

Use the Google Earth navigation controls to adjust the views. Mouse left-click and drag cursor to move. Mouse scroll to zoom in or out. Ctrl-Scroll to rotate. Shift-Scroll to tilt. Double click on the folder to reset the view.

Google Earth print format files are provided for creating maps with legends.†† These can be downloaded from here (save link as:geometric or arithmetic mean layout,†† flow-weighted mean layout ) and loaded via the Google Earth print interface.This shows Total Flow-Weighted Means using the FWM print layout.



Please check the website for updates.


For other displays of Everglades phosphorus data, see:††


Exploratory Analysis of Everglades Flow & Phosphorus Dynamics , December, 2014


Trends in Total Phosphorus Concentration and Flow at Monitoring Sites Within and Upstream of Everglades National Park , September, 2014