Alafia River Minimum Flows and Levels - Southwest Florida Water ...

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2.4 Water Chemistry Although flow can affect water quality, it is not expected that the adoption and achievement of minimum flows will necessarily lead to substantial changes in Alafia River water quality; however, it is appropriate to review the water quality of the Alafia River to fully appreciate how land use changes have affected the river. The Alafia River has experienced high nutrient concentrations and loads rarely encountered in flowing water systems, because of its unique geologic setting and the mining and processing of phosphate ore in its watershed. Examination of water quality data is useful for understanding the complex nature of flow changes in the Alafia River. Long-term water quality changes were evaluated using USGS data gathered at gage sites on the Alafia River proper (near Lithia) and on the North and South Prongs of the Alafia River. Comparison of water quality data with flow records was made for evaluation of relationships between flow and land use. In addition, comparisons were made with sites on other river systems, specifically the Peace River at Arcadia, the Myakka River near Sarasota, and the Withlacoochee River near Holder. The Withlacoochee River in contrast to the Alafia and Peace Rivers exhibits relatively good water quality, perhaps the best of any river system within the District. This is in part attributable to land use differences and in part attributable to inherent differences in geologic setting. Because both the Alafia and Peace River watersheds lie in the Bone Valley geologic formation and because significant portions of both watersheds have been mined for phosphate, it was deemed desirable to evaluate water quality on a river system minimally impacted by phosphate mining. Phosphate mining has occurred historically in the Withlacocchee River watershed, specifically in the Dunnellon-Rainbow River area (which is downstream of the Holder gage), and actually predated mining activities on the Peace and Alafia Rivers. For the following analyses, all available water quality data for selected gages were retrieved from the USGS on-line database. While some data are available on a number of water quality parameters, analysis was restricted to those parameters for which it was felt that a sufficient number of observations existed for inspection of trends. The USGS has long-term flow and water quality data for a number of gage sites throughout the District. Flow records at many sites exceed 50 to 60 years, and some of these have water quality records of 40 years or more. Except for special studies of relatively short duration, water quality at most USGS sites was typically monitored on a quarterly basis at best. Data for each parameter discussed are typically presented in three plots. One plot is a simple time-series plot, which is followed by a plot of the parameter 2-65
versus flow. The third plot typically presented is a plot of the residuals obtained from a LOWESS regression of the parameter versus flow. The last plot is used to evaluate if a parameter loading has increased or decreased over time irrespective of flow. The results of a Kendall’s tau analysis on the residuals was used to help determine if apparent increasing or decreasing trends in a parameter were statistically significant. 2.4.1 Macronutrients: Phosphorus and Nitrogen Concentrations of the two major macronutrients, phosphorus and nitrogen, have been monitored for some time at the Lithia gage site and somewhat less frequently at the North and South Prong sites. The exact chemical form of the nutrient monitored has changed over time (e.g., total nitrate, dissolved nitrate, nitrite+nitrate, etc.), however, for purposes of the discussion that follows and for trend analysis, values for some constituents were combined to provide a sufficient number of data points for analysis. 2.4.1.1 Phosphorus Phosphorus concentrations have been reported by the USGS as total phosphorus, dissolved phosphate, and as ortho-phosphate. For purposes of this discussion, it was assumed that dissolved phosphate and ortho-phosphate are essentially equivalent. Although some of the older data were reported as mg/l phosphate, all values were converted and expressed as mg/l phosphorus (P). As similarly described for the Peace River (SWFWMD 2002), historic P concentrations in the Alafia River and its major tributaries (North and South Prongs) were impressive (see Figures 2-32, 2-33). A record high of 105 mg/l P was reported for a sample collected on the North Prong on April 28, 1969. Considering that background concentrations for a tributary in the Bone Valley area should probably be between 0.1 and 0.5 mg/l P, this high value is 200 to 1000 times higher than should be expected. Although 105 mg/l P is the extreme, values in excess of 20 mg/l were frequently found before 1975 in the North Prong. While considerably improved over past conditions, P concentrations in the neighborhood of 5 mg/l still occur in the North Prong of the Alafia. Fewer measurements have been taken from the South Prong, but it appears that concentrations have never been as high as those on the North Prong. However, concentrations above 1.5 mg/l should not be considered natural for this system. Because the North and South Prongs contribute approximately 81% of the flow (and a combined 72% of the watershed above the gage) as measured at the Lithia gage, it should be expected that concentrations of most constituents should be reflected in concentrations of water samples taken at Lithia. While concentrations greater than 4 mg/l P have not been recorded since 1990, P concentrations have not yet reached levels that would be considered 2-66
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Alafia River Minimum Flows and Leve
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Table of Contents Table of Contents
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4.3.1 HEC-RAS Modeling ............
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Table of Figures Figure 1-1. Buildi
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Figure 2-33. Phosphorus concentrati
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Figure 5-12. Habitat Gain/Loss for
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Table 5-2. Mean elevation, local (c
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flow, with the exception that withd
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Acknowledgement The authors would l
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9) Water quality; and 10) Navigatio
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Water Management District typically
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Peace River at Zolfo Springs, FL. s
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Period of Record Median Daily Flows
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to enhance understanding of histori
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River watershed, to the east by the
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an adjacent area locally known as t
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Water in the surficial aquifer is r
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The Upper Floridan aquifer (UFA) sy
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Figure 2-4. May and September 2001
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head differences indicating breache
Page 41 and 42: data (multiple regression) analyses
Page 43 and 44: 2.2 Land Use Changes in the Alafia
Page 45 and 46: Before discussing individual sub-ba
Page 47 and 48: Table 2-2. Land use and land cover
Page 49 and 50: Table 2-3. Land use and land cover
Page 51 and 52: Figure 2-13. 1972 and 1999 Land use
Page 53 and 54: 2.2.4 Lithia Springs Sub-Basin The
Page 55 and 56: 2.3 Hydrology The assessment of min
Page 57 and 58: Period of Record Median Daily Flows
Page 59 and 60: occurred during the spring were sim
Page 61 and 62: Conversely, since most of the Unite
Page 63 and 64: extending from 1940 to 1969 can be
Page 67 and 68: third highest flow occurred early i
Page 69 and 70: Flow (cfs) Alafia River at Lithia,
Page 71 and 72: 100 North Prong Alafia River at Key
Page 73 and 74: Flow (cfs) South Prong Alafia River
Page 75 and 76: Alafia River at Lithia - Water Qual
Page 77 and 78: South Prong Watershed Above USGS Ga
Page 79 and 80: Comparisons of land use changes and
Page 81 and 82: Comparison of Median Daily Flows fo
Page 83 and 84: Comparisons of Annual 25% Exceedanc
Page 85 and 86: Figure 2-25. Lithia Springs Major b
Page 87 and 88: 2.3.4.3.2 Discharge from Lithia Spr
Page 89 and 90: Relationship Between Lithia Springs
Page 91: Buckhorn Spring Main Discharge (Wit
Page 95 and 96: Alafia River at Lithia, FL Phosphor
Page 97 and 98: While elevated phosphorus concentra
Page 99 and 100: Peace River at Arcadia, FL 20 Phosp
Page 101 and 102: Alafia River at Lithia, FL Nitrate/
Page 103 and 104: 2.4.2 Potassium and Trend Analysis
Page 105 and 106: Alafia River at Lithia, FL 14 Potas
Page 107 and 108: Table 2-10. Results of Kendall's ta
Page 109 and 110: Chapter 3 Ecological Resources of C
Page 111 and 112: 1) maintenance of minimum water dep
Page 113 and 114: flow regimes and these life history
Page 115 and 116: subsidy of water and nutrients that
Page 117 and 118: Chapter 4 Technical Approach for Es
Page 119 and 120: 4.2.1 HEC-RAS Cross-Sections Cross
Page 121 and 122: PHABSIM analysis required acquisiti
Page 123 and 124: Figure 4-5. Upstream vegetation cro
Page 125 and 126: level, whenever possible. Immature
Page 127 and 128: major parameter altered during the
Page 129 and 130: Alafia River - Cross Section 64 - W
Page 131 and 132: Delphi method lacks the rapid feedb
Page 133 and 134: TOTAL DAYS OF INUNDATION DURING THE
Page 137 and 138: Wetted Perimeter - USGS 84.5 - SWFW
Page 139 and 140: Alafia River Station 91.5 Stage in
Page 141 and 142: section sites and corresponding flo
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4.9.1.2 Recreational Use Assessment
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Chapter 5 Results and Recommended M
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greater than 25 cfs would inundate
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For the USGS Lithia gage site, the
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40 35 30 25 20 15 10 T20 T21 T27 T3
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Wetted Perimeter (linear feet) 2000
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dominant vegetation zones, mucky so
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5.5.1 Application of PHABSIM for Bl
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5.5.3 Flow Relationships with Woody
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River begins on October 28 and ends
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Table 5-4. Maximum monthly percent-
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5.6.3 Short-Term Compliance Standar
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Table 5-5. Maximum monthly percent-
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5.8 Short-Term Compliance Standard
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Table 5-7. Proposed Minimum Flows f
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Biological Services Program Report
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Jones, G.W., and Upchurch, S.B., 19
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SDI Environmental Services, Inc. 20
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Upchurch, S.B. and J.R. Littlefield
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A Review of “Alafia River Minimum
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The draft report for setting MFLs f
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methodologies, analyses, and conclu
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The SWFWMD has employed a building
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MFLs for the Alafia and Myakka rive
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RALPH PLOTS AND ANALYSES Recent and
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then used to estimate percent of fl
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necessary. Such a framework should
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to use to meet the criteria of no s
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Shaw, D.T., C.N. Dahm, and S.W. Gol
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The District has added to Chapter 4
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Attachment A June 15 th , 2005 Mrs.
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The Kelly (2004) report includes a
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Figure 1. Box-and-whisker plots of
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As shown in Table 1, a nonparametri
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“augmentation” - be performed a
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Estuary Program 'Restoring the Bala
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APPENDIX D - District's response to
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educed by no more than 8 percent on
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sites with comparable temporal reco
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gradually removed (this appears as
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1) The DISTRICT acknowledges the ma
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Mark Hammond, Director, Resource Ma
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Table 1. Mann-Whitney Statistical A
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Comparison of July Rainfall Totals
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