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Determination of Nutrient Loads to East Coast Canals

Project Proposal for 1999


PROJECT TITLE: Determination of Nutrient Loads to East Coast Canals

PROJECT CHIEF: Arthur C. Lietz
EMAIL: alietz@usgs.gov
PHONE: 305-526-2895
FAX: 305-526-2881




PROJECT SUMMARY: The ecological health of bays and estuaries has become a matter of concern throughout the country. Biscayne Bay, which is a shallow, oligotrophic, subtropical estuary along the southeastern coast of Florida has been adversely impacted in certain locations by the increase in nutrient loads from tributary canals that have resulted from agricultural, urban, commercial and industrial processes. The ecological health of the Bay, as well as development of restoration efforts is dependent in part on understanding loads to the bay. This project will attempt to quantify nitrogen and phosphorus loads to the Bay based upon models developed from ordinary least squares regression techniques and examine which historical methods of sampling accurately represent nutrient concentrations in the water column of south Florida canals. Also, spatial and temporal water-quality trend analysis will be conducted on data from two former National Stream Quality Accounting Network (NASQAN) sites on canals that have a direct impact on the south Florida ecosystem. Information derived from this project will be of immense importance to water managers and planners, particularly in light of recent Everglades restoration plans to restore historical hydropatterns now altered as a result of the extensive water management system.

PROJECT OBJECTIVES AND STRATEGY: This objectives of this project are threefold: 1.) To determine if historical water-quality data collected as grab samples at 0.5 and 1.0 meter below the surface near the centroid of flow adequately represent stream cross-sectional chemistry, and 2.) To develop reliable estimates of nitrogen and phosphorus loads for east coast canals based upon statistical models developed from utilizing the techniques of ordinary least squares regression, and 3.) To summarize water-quality data and determine temporal trends for water-quality constituents at two sites that are strategic to Biscayne Bay and the south Florida ecosystem. During Phase I of the project an intensive field sampling and data collection effort was undertaken. This consisted of the collection of water samples for nitrogen and phosphorus species upstream of coastal discharge points for the major tributary canals. Data collection occurred during various seasons and flow conditions in order to obtain samples truly representative of the hydrologic cycle. Depth-integrated samples collected by the equal-width-increment method as well as grab samples were collected at each canal during Phase I. During Phase II of the investigation, which is now in progress, data analysis and report preparation are being undertaken. This entalls using statistical procedures to compare the two sampling methods and regression analysis in order to develop load models for nitrogen and phosphorus species for each site as well as determining temporal trends at two long-term water-quality sites critical to ecosystem restoration. This analysis will provide important information for the understanding of processes that may have affected water-quality over the years.

Potential impacts and major products: The ecological health of Biscayne Bay is dependent on nutrient loads. Understanding the hydrologic processes that control nutrient loadings to the Bay is necessary in order to properly develop restoration efforts. In order to accomplish this, reliable estimates of loads to the Bay are necessary. Much of the nutrient data that have been collected historically has been from point samples by the Dade County Department of Environmental Resource Management. The degree to which these samples adequately represent nutrient concentrations within the water column of the canals of south Florida is presently unknown and limits confidence in loading estimates. Furthermore, the relationship between flow and concentration that occurs in natural, uncontrolled streams in other parts of the country may not apply to the artificially controlled canals of south Florida. Both of these issues need to be addressed in order to develop nutrient budgets and to plan effective restoration strategies now and in the future. Also, water-quality trend analysis on data collected at two former NASQAN sites will provide insight into processes that have affected nutrient and pollutant loading to the Bay as well as the south Florida ecosystem as a whole. Information documented as a result of this project will provide water managers and planners critical information that is relevant to the restoration of historical hydropatterns in the south Florida ecosystem and in particular to the plans for the diversion of water from the agricultural/urban corridor to Everglades National Park. Major products include two reports: ěPredictive Models for Estimating Nitrogen and Phosphorus Loads from East Coast Canals to Biscayne Bay,î currently in review and ěAnalysis and Interpretation of Water-Quality Trends at two former NASQAN Sites, 1966 -1994.î which will be completed during the 1999 water year.

COLLABORATORS AND CLIENTS: During the duration of the project close collaboration and exchange of technical information has been and will continue to be maintained with other projects of the South Florida Ecosystem Restoration Initiative, particularly the Fresh Surface Water Discharge to the East Coast project. This project used the Acoustic Doppler Current Profiler to develop discharge ratings for the east coast canals. Also close collaboration with the south Florida NAWQA program and other agencies such as the U.S. Army Corps of Engineers will continue. This investigation has interfaced closely with the south Florida NAWQA program in that it has contributed to the process of defining the relationship between land use and water quality conditions and helped identify water quality trends in south Florida. Coordination of sampling efforts and exchange of information will also be maintained and continued with DERMís Biscayne Bay monitoring program. Determination of nutrient loads to Biscayne Bay and long-term trends at NASQAN stations will aid regulatory agencies such as SFWMD and DERM in water resource management particularly with proposed plans to redirect flow from the urban/agricultural corridor to Everglades National Park. Logistical support in gaining access to control structures during sampling -events was provided by the SFWMD field offices.

TIMELINE (FY1999 to project end)
MAJOR TASKS: 1999 water year: Data review and data interpretation of two former NASQAN sites, Miami Canal and Tamiami Canal.
1999 water year: Report preparation and publishing of trend analysis report.
1999 water year: Data collected during the entire study will be archived in a special database in conjunction with the Ecosystem Database Development project.
1999 water year: Two page synopsis will be prepared that summarizes accomplishments of project, its relevance to management issues and recommendations for future studies.
DELIVERABLES: 1999 water year: Progress reports - October, February and June.
1999 water year: Interpretative report.
1999 water year: Synopsis will be prepared as a fact sheet.
PRODUCTS: 1999 water year: Interpretative report entitled: ěAnalysis and Interpretation of Water-Quality trends at Two Former NASQAN Stations, 1966 - 1994.î
1999 water year: Fact sheet synopsis report.

FY 1999 ACTIVITIES: During the 1999 water year a interpretative report will be prepared, reviewed and published. This report will entail the determination of temporal trends at two long-term surface water sites that are critical to ecosystem restoration. Both of these sites, Miami Canal at S-26 and Tamiami Canal - forty mile bend to Monroe, were part of the NASQAN program. Data collected from Miami canal under the NASQAN program spans the years 1974 to 1994. Data collected from Tamiami canal under the same program includes the years 1978 to 1993. However, considerable water-quality data exists from both sites since 1966. The methods to be used in determining trends at these two sites are documented in the report entitled, ěThe Computer Program Estimate Trend (ESTREND), a System for the Detection of Trends in Water-Quality Dataî by Schertz, Alexander and Ohe (1991). This program contains methods for dealing with the two main causes of unwanted variation in water-quality data: seasonality and effects of discharge. The program documents a non-parametric statistical approach to dealing with water-quality data by applying the Seasonal Kendall Trend test to flow-adjusted residuals determined by developing statistically significant concentration/discharge models on specific parameters where possible. Statistically significant trends may be determined on unadjusted concentration data as well as flow-adjusted concentration data, whichever provides the best trend result as determined by a significance level (p-value) of <0.10. The program will determine trend slopes for specific parameters when a statistically significant trend is determined. The program provides methods for dealing with censored as well as uncensored data. Summary and descriptive statistics for specific parameters will also be included in the final interpretative report as well as maps with spatial symbols indicating uptrends, downtrends or no trends. Locally weighted scatterplot smoothing (LOWESS) will also be used to describe the non-linear, short-term variations that have occurred in the data over the period of record. A synopsis report will be prepared that summarizes results of the investigation, its relevance to management issues and collaboration with other agencies and recommendations for future studies

FY 1999 DELIVERABLES/PRODUCTS: The report entitled ěAnalysis and Interpretation of Water-Quality Trends at Two Former NASQAN Stations in South Florida, 1965-1994î will describe the project study area including the physiography, climate, population, land use and the flow regime of south Florida. Data collection methods and procedures will also be described as well as sample processing and preservation. Methods for the determination of water-quality trends will be described including methods for dealing with variation in water-quality data caused by the effects of streamflow and seasonality. Criteria for determining trends on censored and uncensored data will be described. An analysis and interpretation of water-quality trends will be made on physical properties and field measurements, major inorganic constituents, nitrogen and phosphorus species, suspended sediment and bacteriological parameters. A two page synopsis will be prepared describing in detail project accomplishments, its relevance to management issues and to future studies.

FY 1999 OUTREACH: Outreach will be directed to other federal agencies such as the U.S. Army Corps of Engineers as well as state agencies such as the South Florida Water Management District and local agencies that have an interest in the health of the south Florida ecosystem, particularly the Dade County DERM which has regularly collected nutrient data on east coast canals. Outreach will also include the production and dissemination of a two page synopsis report as a fact sheet that summarizes project accomplishments.


FY 1998 ACCOMPLISHMENTS AND OUTCOMES, INCLUDING OUTREACH: The first draft of an interpretative report entitled ěPredictive Models for Estimating Nitrogen and Phosphorus Loads from East Coast Canals to Biscayne Bay, Dade County, Florida, 1996-1997î was completed and is currently in review. This report is based on data collected during the 1996 and 1997 water years. Non-interpretative sections of a second report on determining temporal trends on water-quality data from two long-term water quality stations are in progress. Periodic progress reports have been prepared and distributed to interested clients and collaborators. Outreach has included contacts and close association with the south Florida NAWQA program as well as with other agencies, both federal, state and local that have an interest in the Everglades ecosystem restoration. particularly the Dade County Department of Environmental Resources Management and the South Florida Water management District.

FY 1998 DELIVERABLES, PRODUCTS COMPLETED: First draft of interpretative report mentioned in the previous section was completed and is in review.

Names and expertise of key project staff: Arthur C. Lietz, water-quality specialist, project chief, Kimberly Swidarski, cartographic technician

Other required expertise for which no individual has been identified: None

Major equipment/facility needs: None

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