Protecting the ecological integrity of our nations waters: An analysis of water quality monitoring data

Background/Question/Methods

Through its anti-degradation standard, the Clean Water Act (CWA) provides States with a mechanism for maintaining the chemical, physical, and biological integrity of the Nation’s waters. In the State of Florida, the Outstanding Florida Water (OFW) designation carries this anti-degradation standard. There are 350 OFWs in the state.  The goal of this research is to determine:

1. To what extent OFWs waters are listed as impaired;
2. Sufficiency of water quality monitoring data in OFWs;
3. Water quality trends in OFWs between 1990 and 2011;
4. Whether the OFW designation protects designated waters from degradation. 

Water quality impairment data was extracted from the Florida Geographic Data Library and analyzed using GIS software.  To assess water quality trends and data sufficiency, phosphorus, nitrogen, and chlorophyll-a data for 80 inland flowing OFWs was extracted from Florida STORET.  Sampling locations having data spanning 10 years with at least 3 seasonal samples per year were considered sufficient for determination of water quality trends.  For all data sets, duplicates, field replicates and blanks were removed, and non-detect values were replaced with the MDL. JMP software was used to conduct statistical analyses (linear regression, ANOVA, Tukey- HSD, and Wilcoxon tests) on 230 data sets fitting the criteria.

Results/Conclusions

Determinations of water quality monitoring data sufficiency show that of the 80 OFWs assessed in this study: 13 had no data available; 25 had less than 1 to 3 years of data; 12 had 5 to 9 years of data; and 30 had 10 or more years of data.

Analyses of water quality show:

1. 87% are listed as impaired waters under Section 303(d) of the Clean Water Act and F.A.C.  62-303.  Of those impairments 35% are due to high concentrations of mercury in fish tissue, 20% are due to high levels of nutrients, 17% are due to high concentrations of coliforms, 14% are due to low levels of dissolved oxygen, 4% are due to high levels of bacteria, and 8% are due to high levels of other metals. 
2.  4% have water quality data showing a statistically significant decline in water quality, suggesting that they may not be in compliance with the Florida OFW anti-degradation standard as set forth in F.A.C. 62-302.700.  

These results indicate a need for the improved collection of water quality data in regular seasonal intervals across time to support the regulatory protection of our Nations waters as set forth in the Clean Water Act.