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Environmental Health Laboratory Water Quality Data

Page last updated: 08/16/12

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Volusia County Water Quality Results

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It is widely held that water quality is a relative measure used to describe the condition of a waterbody relative to human needs or values; and thus the use of the terms “good water quality” or “poor water quality” is not absolute.

Water quality can be judged by different people in different ways. What one person sees as a good “fishing hole” having abundant vegetation and aquatic fauna, might not be as appealing to swimmers. Water quality is not an absolute science; quality is based upon the proposed use of that water.

These value judgments are most often related to the extent to which a waterbody may be meeting expectations of how it can be used and what its characteristics should be.

Water quality standards for waterbodies of the state, including lakes, rivers and streams, springs, estuaries, as well as coastal areas, have been developed by the Florida Department of Environmental Protection (FDEP) and are used in conjunction with the Impaired Waters Rule (FS 62-303) to assess state waters. Additional information may be found at http://www.dep.state.fl.us/water/. We appreciate any comments you may have.

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Executive Summary

Florida’s surface waters are an extraordinary natural resource that includes lakes, rivers, streams, bays, and estuaries. The increasing economic development of our coastal area is due to the natural beauty of these estuaries. Our waters are used for recreation, commercial and recreational fishing, and shellfish harvesting to name a few. They are an invaluable source as a natural habitat for most of Florida’s native flora and fauna.

Due in part to the constant changes to Florida’s environment through development, and in addition to our ever-growing population, these resources have become endangered and it has become necessary to monitor the health of our surface waters.  

The Volusia County Environmental Health Lab (VCEHL’s) surface water program is committed to continue identifying and documenting the conditions of our surface water resources as well as determining possible trends in water quality.
Our enormous amount of data is available to everyone through a comprehensive water quality information system. The data is stored in the United States Environmental Protection Agency (USEPA’s) STORET (Storage and Retrieval) database. 

Based on the Water Quality Index (WQI), the trend analysis is only an indicator in determining the water quality. Indices have been developed to summarize multiple water quality monitoring parameters into a single numerical value.  This value represents a ‘grade’ or ‘score’ for a particular water body location and rates the water’s condition as either good, fair, or poor.

Forward thinking along with the progressive development of the entire infrastructure will be necessary in order to obtain effective solutions and protection against any further degradation of the fragile environment.  The impact and depravation that our future generations will have to endure is unimaginable.

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Surface Water Program

Since 1992, the Volusia County Environmental Health Lab (VCEHL) has collected water samples from the watersheds of Volusia County such as the Halifax River, St. John’s River, Mosquito Lagoon, the springs in West Volusia, and numerous lakes. In order to provide the public with these results and to help locate water body areas that need improvement, the VCEHL has summarized the historical surface water data and produced graphs of these analyses.

The graphs will help assess whether or not there have been any changes in the surface waters. They will also help assess whether or not any significant long term changes or trends are developing within the water body over time.

Results of the water quality analyses are also periodically reported to the United States Environmental Protection Agency (USEPA) and are stored into a large database system called STORET. This is a storage and retrieval system of water quality data for surface waters throughout the nation. This Data can be accessed at the USEPA’s web site www.epa.gov.

When analyzing the quality of surface waters, there are many factors to consider. Guidelines have been established for certain parameters such as bacteriological and nutrient levels, which can indicate if pollution is adversely affecting the area where a water sample was collected.

Two types of pollution affect our surface waters: Point source, and non-point source pollution. Point source pollution is identifiable as a specific discharge from industrial facilities, landfills, septic systems, sewage treatment plants, and other facilities. Non-point source pollution includes storm water and other sources which are non-specific, the actual sources of this type of pollution are unlikely to be determined.

Storm water is the runoff from developed urban and agricultural areas. As rainfall flows across yards, streets, parking lots, animal lots and fields, it picks up many contaminants, dumping them into waterways and wetlands through storm drains, pipes and ditches. In both urban and agricultural storm water, elevated nitrogen and phosphorus levels are discharged into the receiving water body from fertilizers and animal wastes that alter the natural balance of these nutrients. These elevated nutrient levels result in the growth of algae, which can ultimately lead to oxygen depletion in the water and kill aquatic life.

Agricultural storm water runoff is especially serious when it enters slow-moving rivers or bodies of water with little or no water circulation such as canals and lakes. Even rainfall can act as a non-point source pollutant when it becomes acidic (‘acid rain’) as a result of sulfates and nitrates being released into the air from auto exhausts and industrial emissions.

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Water Quality Trends

The grades for the health of Volusia’s surface waters are determined using a variation of the Water Quality Index (WQI) developed by the State of Florida (Hand, 2000).  The WQI is a mathematical method consisting of condensing several parameters into a single numeric value to summarize the overall status of the water body.

Three categories of water quality parameters are used in the local implementation of the WQI:

  • water clarity (turbidity and total suspended solids)
  • nutrients (total nitrogen and total phosphorus)
  • bacteria (fecal coliform)

The individual parameters are averaged to obtain an overall index value for each category.  The scores are obtained by transforming the data annual averages with the state’s formulas log function (i.e. LN function).  The index values for each of the categories is then combined in a weighted formula to obtain the final WQI rating (good, fair, or poor) for each water monitoring location in the water body.

Due to the unique natural chemical and biological conditions that make up each type of water body, the cut-off values have been adjusted to reflect these specific differences.  The original WQI was formulated for estuarine systems.  The adjustment factors were based on the water quality percentiles from the State data set.   Over the years, the Florida Department of Environmental Protection (FDEP) has modified the WQI to accommodate backwater, streams, and springs.  The WQI for streams was used in the assessment of the St. John’s River Project. 

The State of Florida’s implementation of the WQI is applied to the entire water body, but the local adaptation of this WQI provides data for individual stations within each water body.   In Volusia County, approximately one hundred water-sampling stations are currently being sampled.

Hand et al. (1996) summarizes the Florida Water Quality Index (WQI) has the following advantages compared to other indices:

  • It is based on the percentile distribution of Florida stream data.
  • It is tailored to Florida.
  • It uses the most important measurements of water quality in Florida (clarity, dissolved oxygen, and oxygen-demanding substances).
  • It identifies areas of good, fair and poor water quality that correspond to professional and public opinion.
  • It eliminates subjective assessments and individual biases in assessing water quality.

To be consistent with the State’s approach for the waters statewide, we take all the data and put it together; then;

  • Sort it by the column with the WQI data on ascending (or descending order if preferred).
  • We then determine the total number of records.
  • For example, we have a total of 518 records for estuaries to date, divided by 10 equals 51.8, which is 10 percent of the observations.
  • Ten percent of the observations (51.8) times two (2) equals 103.6.  Therefore, the cutoff value for the lower 20% of the observations is the first 103 observations approximately, which is the “excellent” range or 21 to 58 percent.
  • Likewise, the following 59 percent to 66 percent range would be indicated as good, 67 percent to 73 percent as fair, and the lower 20 percent as poor.

In other words, rather than assigning a predetermined range, we base that data on each individual water body, by using as break-points the values for the best 20 percent as “excellent”, 21 to 66 percent as “good”, 67 to 73 percent as “fair”, and the lower 20 percent as “poor”.  This approach is very similar to the approach taken by Florida Department of Environmental Protection for the entire state, which is consistent with statistical practice.

Since the first 114 “excellent” observations might overstate the quality; we grouped the first 114 “excellent” observations under the following category, which entails the following 21 to 66 percent of the observations or “good” category.  We were able to justify where the cutoff values were placed for the last 16 years worth data in order to explain the particular problems facing the surface waters in the County of Volusia.

The WQI provides a means to establish a water quality data trend for the past 15 years. It provides a generalized way to interpret water quality data that is quick and useful.  It has been accomplished by evaluating the results of each monitoring station in order to establish the water quality trend for every surface water sampling year.

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Page last updated: 08/16/12