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Analysis of Historical Water-Quality Data

photo of a pond in everglades national park
Project Investigator: Benjamin F. McPherson

Project Personnel: Ronald Miller, Arturo Torres

Project Start Date: 2001 End Date: 2005

Recent Funding: (FY05) USGS GE PES


The project calls for a comprehensive analysis of historic water-quality data collected in Everglades National Park (ENP), Big Cypress National Preserve (BICY) and other DOI lands in south Florida.


The Greater Everglades ecosystem is a unique subtropical network of diverse habitats that encompasses a large part of the southern Florida peninsula. Part of the area - mostly publicly controlled parks, preserves, sanctuaries, and refuges managed as Department of the Interior trust resources - remains in nearly undeveloped, natural or near-natural condition, while much of the area has been dramatically changed due to major urbanization and agriculture. Water is the principal driving force within this system, and supplying sufficient water to support these diverse habitats is a continuing challenge for water and resource managers. The major changes to the natural flow system have had a profound effect on the natural habitat and have driven some organisms - such as the Florida panther - to the brink of extinction.

The principal human factors affecting the Greater Everglades ecosystem and competing for fresh water are population growth and expanding urbanization, and agriculture; factors that did not exist a little more than 100 years ago. In the mid-1800's, South Florida was a lush, subtropical wilderness, with few inhabitants. The Kissimmee-Okeechobee-Everglades watershed provided the fresh water that sustained high terrestrial and coastal productivity. The conflict of human versus natural elements in South Florida began in earnest in the early 1900's when draining the wetlands was first considered essential for commerce and human safety. Loss of life due to hurricane-related flooding in the 1930's accelerated drainage projects, culminating with Congressional authorization of the Central and Southern Florida (C&SF) Project in 1948.

Environmental impacts of these changes, coupled with the demand for fresh water, include alteration of flow patterns; soil loss and subsidence due to agriculture and drainage; degradation of water quality including nutrient enrichment and contamination by pesticides and mercury; fragmentation of the landscape and the loss of wetlands and wetland functions; impairment of estuarine and coastal resources; and significant declines in native plants and animals, as well as widespread invasion by exotic species.

In recent years, more than 30 Federal, State, and local agencies, Native American Tribes, and environmental groups have partnered to restore, to the extent possible, critical functions to the Greater Everglades ecosystem and, at the same time, provide for the many other needs of South Florida. That plan is embodied in the Comprehensive Everglades Restoration Plan (CERP) of the U.S. Army Corps of Engineers (USACE), the goal of which is to improve the quantity, quality, and timing of delivery of water to this ecosystem. This massive and unprecedented program would cost nearly $8 billion and take more than 30 years to complete.


Figure 1. Map showing hydrologic monitoring stations. [larger version]
Everglades Restoration will result in modifications of water flows into the Everglades and its coastal waters. Major questions exist on how these modifications may affect water quality, including sources and processes that affect nutrients and their availability, the distribution and remobilization of pesticides into the food web, and on chemical processes such as changes in sulfur concentrations to those more conducive to the production of methyl mercury and ultimately the buildup of mercury in the food web.

To understand changes in water quality that may result from Everglades restoration, it is essential to know historic baseline water-quality conditions, how water quality may have changed, and what the current conditions are. This project provides information to assess these aspects of water quality using data that have been reviewed and edited for errors and inconsistencies, including seasonal and long-term trends, and potential sources of water-quality problems in the Everglades.

This project will provide a review and analysis of historical water quality data in Big Cypress National Preserve, Everglades National Park, and other DOI lands in south Florida. This information will help establish water-quality standards and baseline conditions in the parks and preserves, and will help evaluate the potential effects of CERP on water quality. Objectives include: (1) assemble water quality data; (2) review and edit the data and provide a working data base; (3) analyze and evaluate the data and prepare interpretative reports on baseline water-quality conditions and trends in BICY and EVER in 2003, Loxahatchee National Wildlife Refuge (LNWR) in 2004, and Biscayne Bay National Park (BBNP) in 2005.

Big Cypress National Preserve (BICY) and Everglades National Park (EVER) maintain separate networks of hydrologic monitoring stations (hydrostations) for measuring the stage and quality of surface water throughout their areas of responsibility (Figure 1). The data collected at these sites provides a historical baseline for assessing hydrologic conditions and making a wide range of management decisions. Surface-water stage data is relatively straight-forward to analyze, and has typically been conducted by in-house hydrology staff. Analysis of surface water-quality data is generally regarded as being more complex because of the subtleness of trends, absence of continuous data (bi-monthly for BICY and monthly for EVER), and dependence on surface water depth and season. In addition, changes in analytical methods and reporting levels can complicate trend analysis and give false trends for chemicals occurring near their reporting levels such as phosphorus.

Collection and analysis of water-quality samples at BICY and EVER are done under cooperative agreements with the South Florida Water Management District (SFWMD). Under these agreements, Park Service employees collect the samples in the field and SFWMD personnel provide provide sampling equipment and laboratory analyses. EVER has been sampling water quality on a monthly basis since 1984 at 9 "internal marsh" stations as part of this program. BICY has been sampling water quality on a monthly basis at 10 "internal" stations since 1995 as part of this agreement, with water quality data at these sites extending as far back to 1988 under a different agreement. Water-quality data collected at the BICY and EVER stations has been archived and reported for short-time intervals (yearly and bi-yearly), but an analysis that covers all sampled parameters, extends over the full period of record, and provides comparisons between the two units has yet to be performed.

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Script last updated: 23 October 2018 @ 12:03 PM by THF. Record creator: BJM. Record last updated by: LJT.