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Work Plan: Water Quality Monitoring and Modeling for the A.R.M. Loxahatchee National Wildlife Refuge: 2004-2006

Prepared by: Laura A. Brandt, Matt Harwell, Mike Waldon
March 29, 2004


(Note: entire PDF is available for download below)

In FY04, Congress specifically appropriated $1,000,000 to the Arthur R. Marshall Loxahatchee National Wildlife Refuge for water quality monitoring and modeling. This work plan outlines the studies that will be conducted in three areas that will improve the scientific understanding of water quality issues in the refuge and will provide information that can be incorporated into water management decisions for better protection of refuge resources. A draft of the work plan was developed by refuge staff and provided to State, other Federal, and Tribal partners for revie w and comment in February 2004. This version incorporates comments received in February and March 2004.

The three areas of the plan are: increased monthly water quality sampling sites, similar to current monthly sampling; conductivity transects to provide a better understanding of how and when water from the canals moves into the interior marsh; application of hydrodynamic and water quality modeling to the refuge.

These three areas are consistent with long-term goals identified in the refuge’s 15 year Comprehensive Conservation Plan (USFWS 2000) and recommendations made by the Technical Oversight Committee for addressing exceedances observed in interim phosphorus levels within the refuge.

Three existing monitoring networks (monthly compliance monitoring, monitoring at inflow and outflow structures, and 11 stations along two transects in the southwest) operated by the Sout h Florida Water Management District (SFWMD) regularly monitor water quality within the refuge. The current marsh network is estimated to cover approximately 60% of the refuge, leaving 40% of the marsh uncharacterized. The uncharacterized areas of greatest concern are those between the canals and existing stations and in the immediate vicinity of existing or proposed structures (STA-1E and STA-1W for example). The additional monthly sampling will focus on these uncharacterized areas. Forty additional stations will be sampled starting as early as May 2004. Thirty of the sample sites will be located on six transects extending from the canal to 4 km into the interior. Ten additional points will be located in the northwest and southeast. Data collected at these stations will include parameters consistent with the existing Everglades Protection Area (EVPA) sampling.

Much of the Everglades, including the refuge, developed as a rainfall-driven system with surface waters low in nutrients and inorganic ions suc h as chloride, sodium, and calcium (low conductivity). Information from the refuge and other wetlands indicates that changes in major ions may cause undesirable ecological changes in flora and fauna. It is known that canal water has high conductivity compared to the marsh interior (1000 µS vs, 100 µS, respectively) and there is concern that increases in canal water intrusion into the refuge interior may cause negative ecological consequences. Four to six transects outfitted with data sondes set to collect conductivity and temperature data at hourly intervals will be established in March-May 2004 near locations where water may flow into the marsh in order to documents changes in conductivity adjacent to the canals and in response to water management operations. This information can then be used to refine operations when possible, to minimize canal water intrusion into the interior. Synoptic sampling also will be conducted around the transects when water stages are at specified conditions in order to better understand canal water intrusion.

The goal of the modeling portion of this project is to provide support for refuge management decisions and planning related to water control operations, water supply, and water quality. Calibration and verification using historic and new monitoring data will be used to characterize the applicability, credibility, and uncertainty of the model or models implemented. Scenario analyses will be performed providing detailed projections of the consequences on hydrology and water quality of various management alternatives. Finally, the refuge will be provided with a model that will be maintained to support future management decisions, and provide a foundation for future model development, monitoring planning, and ecological studies.

The information collected during these studies will help resource managers identify potential threats to refuge resources, keep unimpacted areas from becoming impacted, maximize the potential for the recover of impacted areas, and better understand the hydrology and ecology of the refuge.


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