(7.7) WATER DATA - Important Excerpts from Technical Publication SJ2016-1
Important Excerpts from
"Technical Publication SJ2016-1"
"Effects on Lower St. Johns River Nutrient Supply and TMDL Target Compliance from the Restoration of a Free-Flowing Ocklawaha River"
by John Hendrickson of the St. Johns River Water Management District
An Information, Opinion, & Sources Report
Compiled by "Ocklawahaman" Paul Nosca
Created: 03 June 2016
Last Revised: 04 July 2018
Hendrickson, J. 2016. Effects on Lower St. Johns River Nutrient Supply and TMDL Target Compliance from the Restoration of a Free-Flowing Ocklawaha River. Technical Publication SJ2016-1. 107 pages. St. Johns River Water Management District, Palatka, Florida.
"Ocklawahaman" Paul Nosca -- while highly recommending that SJ2016-1 should be reviewed in its entirety -- especially considers these selected parts of Mr. John Hendrickson's EXCELLENT research paper to be VERY IMPORTANT reading for all those who would favor the restoration to free-flowing again "Source to the Sea" of the 56-mile Ocklawaha River-Silver River-Silver Springs mainstream system of north-central Florida which would only be made possible by the breaching of Rodman (Kilpatrick) Dam.
The following text (in italics) is excerpted -- copied exactly -- from various paragraphs and sections of "Technical Publication SJ2016-1":
This report details the results of analyses performed by the St. Johns River Water Management District about the possible downstream effects of restoring of the lower Ocklawaha River to a free-flowing condition by removing the Rodman Reservoir. The analysis represents the most comprehensive reassessment to date focusing on the changes in nitrogen and phosphorus export from a free-flowing Ocklawaha River. The original assessment, conducted in 1994 as part of the Environmental Studies Concerning Four Alternatives for Rodman Reservoir and the Lower Ocklawaha River (ECT, 1994) predicted that the removal of Rodman Reservoir would significantly increase nutrients, in particular, nitrate-nitrogen, delivered to the lower St. Johns River Estuary. With the application of additional data and improved modeling capabilities, this report yields more accurate findings intended to inform interested parties about likely outcomes of restoration.
New information about the role of nitrogen in worsening eutrophication in the lower St. Johns River that was not known at the time of the restoration permit submittal has greatly influenced the findings of this study. Monitoring data indicate that the availability of nitrogen alone (i.e., without the addition of phosphorus) does not encourage algal bloom growth in the freshwater reach of the lower St. Johns River and therefore does not constitute an adverse environmental impact from restoration. In addition, while phosphorus remains the controlling nutrient for algal blooms in this reach, this analysis suggests that on average just eight additional tons of phosphorus would be added annually from restoration efforts. While phosphorus reduction elsewhere would presumably be necessary to mitigate the effects of that increase, the offset of a load of this magnitude should be attainable through the use of current technology in several nearby water bodies, including the middle St. Johns River, Lake George, or the freshwater portion of the lower St. Johns.
In 1991, federal de-authorization of the Cross Florida Barge Canal Project resulted in the transfer of canal lands to the state of Florida. An ad hoc Canal Lands Advisory Committee (CLAC) was formed to provide recommendations to the Governor and Cabinet on the disposition of the barge canal lands and structures. After deliberating on the recommendations of the CLAC, the 1993 Legislature passed Chapter 92-213, Laws of Florida, which directed the Department of Natural Resources (now the Florida Department of Environmental Protection [FDEP]) to “ . . . study the efficacy, both environmental and economic, of complete restoration of the Ocklawaha River, partial restoration of the river, total retention of Rodman Reservoir, and partial retention of the reservoir . . ..” Funds were provided for the St. Johns River Water Management District (SJRWMD) to undertake the study of these four alternatives. As part of the comprehensive assessment performed by SJRWMD, Volume 11 of the Environmental Studies Concerning Four Alternatives for Rodman Reservoir and the Lower Ocklawaha River, Surface Water Quality and Alternatives Analysis for Rodman Reservoir (ECT, 1994) predicted a post-restoration increase in nitrogen (in the form of nitrate+nitrite-N) and phosphorus (as orthophosphate) loads of 878 and 30 metric tons/yr to the LSJR.
Despite the predicted increase in downstream nutrient load, the positive aspects related to the restoration of floodplain functions, increased unique habitat and migratory fish passage appeared to provide overall net environmental gain. At the directive of then-Gov. Lawton Chiles and the Florida Cabinet, FDEP in 1997 submitted a permit application to SJRWMD for the removal of Rodman Reservoir to restore a free-flowing lower Ocklawaha River.
But in 1999, once the permit application package was complete, the case for the restoration was deemed insufficient to meet the environmental resource permit (ERP) and consumptive use permit (CUP) public interest tests, and SJRWMD staff informed FDEP that they could not recommend approval to their Governing Board. The most prominent concern contributing to the recommendation of denial centered on the potential adverse impacts of increased nutrient load to the lower St. Johns River. Adding to this concern was the fact that the lower St. Johns at the time was one of the most prominent water bodies included on the 1999 consent decree between the U.S. Environmental Protection Agency and Earthjustice to establish Total Maximum Daily Loads (TMDLs) for impaired Florida waters. FDEP requested that SJRWMD not take agency action and to hold the permit in abeyance indefinitely, a status which has continued until this day.
This analysis estimates that a free-flowing Ocklawaha River will increase the average TP load to the lower St. Johns River by 11.5 metric tons (MT)/yr in reservoir-full years, and by 0.1 MT/yr in drawdown years. If drawdowns are conducted once every three years (the 2012 and upcoming 2015 drawdowns were both postponed a year hence will have been conducted on 4-year cycles), then the long-term median discharge condition phosphorus load increase under a free-flowing Ocklawaha River will be 7.7 MT/yr. To put this load in context, the allocated domestic wastewater phosphorus load to the freshwater lower St. Johns River is 12.4 MT/yr, and the annual load from the Georgia Pacific Palatka Mill was estimated in 2011 to be 11.5 MT/yr (LSJR BMAP, 2011). The Tri-County Agricultural Area (TCAA) delivers an average annual estimated phosphorus load of 84 MT/yr (FDEP, 2008). Two of the SJRWMD-designed and built regional stormwater treatment systems in the TCAA together removed an annual average of 4.5 MT/yr (2009–2014; Livingston-Way, 2014 Draft BMAP). And, since 2012, SJRWMD has conducted a gizzard shad harvest program on Lake George which has annually removed approximately 4.6 MT/yr. So the predicted phosphorus load increase from a free-flowing lower Ocklawaha, while not insignificant, is in the range of other permitted phosphorus loads to the LSJR, and within the realm of reduction achieved by projects currently functioning elsewhere in the basin. Should FDEP choose to pursue this restoration, and if a mitigation were deemed appropriate to offset potential harm based on the predicted phosphorus load increase, it would likely be achievable through a combination of treatment project options directed elsewhere in the middle St. Johns, Lake George, or the freshwater LSJR. This fact, combined with the understanding of adverse impacts that accompany reservoir drawdowns, a necessary management action for the maintenance of the reservoir (Hendrickson et al., 2016), appears sufficient such that a recommendation of denial, on the grounds of the detrimental impacts to downstream water quality, is no longer a certainty for this restoration permit.
"One striking feature of the annual pattern is the consistency with which diminishing concentrations of NOx, and also dissolved silica (SiO2), are associated with the increase in the relative abundance of N-fixing cyanobacteria. Silica is also a fundamental regulator of phytoplankton community structure in the Lake George and the LSJR, as it is an essential growth element for diatom algae, the natural dominant group for a lacustrine blackwater river such as the St. Johns. For these same four NOx-spike years (as well as other years not shown), N-fixing cyanobacteria appear in the phytoplankton community shortly after NOx and dissolved SiO2 are very low and essentially depleted (Figure 27). Phytoplankton biomass continues to increase after the depletion of these nutrients, with N-fixing cyanobacteria the beneficiary of the niche created by the depletion of inorganic N and silica."
"While data presented here clearly show the capability of Rodman Reservoir to retain nitrogen, during times of the year it appears also to be a significant sink for dissolved silica. Comparison of above and below-reservoir monthly mean SiO2-D concentration indicates that from December through June, while the reservoir is full, SiO2-D concentrations at the head of the reservoir are significantly greater than those at the mouth (Figure 29). In drawdown years, SiO2-D at the mouth greatly exceeds the reservoir condition, and even appears greater than the inflowing concentrations, indicating the possible mobilization of reservoir or floodplain stored SiO2."
"These observed data suggest that additions of NOx of the magnitude expected from the restoration of the LOR will not increase LSJR freshwater reach phytoplankton standing stock. Reduction of nitrogen alone has been shown to be ineffectual to control eutrophication in freshwater lakes (Schindler et al., 2008; Havens et al., 2002), and it has been hypothesized that the retention of silica in reservoirs has contributed to the dominance of cyanobacteria in downstream waters (Koszelnik and Tomaszek, 2008; Ittekkot et al., 2000). The addition of NOx and dissolved SiO2 may instead have the effect of delaying the community succession from the late winter community of eukaryotic algae, primarily composed of diatoms, to N-fixing cyanobacteria, and patterns in the phytoplankton community composition in the LSJR and Lake George tend to support this. For phytoplankton community composition data collected at the long-term freshwater monitoring sites in Lake George and the freshwater LSJR, the mean January–March (coincident with drawdown-year low pool phase) NOx concentration is inversely correlated with spring bloom cyanobacteria biomass (Figure 30). These relationships suggest that the increased supply of NOx, and possibly also SiO2, associated with a FFR scenario would not result in increased downstream phytoplankton biomass, and may actually improve the quality of the LSJR pelagic food chain, by counteracting the adaptive advantage of N-fixing cyanobacteria and encouraging the growth of beneficial eukaryotic algae in the phytoplankton."
CONCLUSIONS AND RECOMMENDATIONS
In both the Upper Ocklawaha and Lower St. Johns River basins, lake restoration projects and removal and improved treatment of point and nonpoint sources of nutrient pollution has resulted in reductions in TP concentration and significant amelioration of eutrophication of the affected aquatic ecosystems (Ceric and Winkler, 2014; Fulton, 2014; FDEP, 2014). This assessment of FFR nutrient load to the lower St. Johns River is based on models developed on the conditions that existed from the mid 1990s through 2012, incorporating historic data from a time when loading rate was much greater, hence the models may overestimate the nutrient loads and receiving water body conditions that exist presently and in the future. This fact, along with the conservative assumptions built into the downstream delivery calculations, would lead one to expect that the downstream algal biomass increases under a free-flowing Ocklawaha River will be less than portrayed based on conservative mixing load and concentration increases.
This analysis estimates that a FFR will increase the TP load to the LSJR by 11.5 MT/yr in reservoir-full years, and by 0.1 MT/yr in drawdown years. If drawdowns are conducted once every three years (the 2012 and upcoming 2015 drawdowns were both postponed a year hence will have been conducted on 4-year cycles), then the long-term median discharge condition TP load increase under a FFR will be 7.7 MT/yr. To place this in context with other TP loads, the allocated domestic wastewater TP load to the freshwater LSJR is 12.4 MT/yr, and the annual load from the Georgia Pacific Palatka Mill was estimated in 2011 to be 11.5 MT/yr (LSJR BMAP, 2011). The Tri-County Agricultural Area (TCAA) delivers an average annual estimated TP load of 84 MT/yr (FDEP, 2008). Two of the SJRWMD-designed and built regional stormwater treatment systems in the TCAA together removed an annual average of 4.5 MT/yr (2009–2014; Livingston-Way, 2014 Draft BMAP), while the rough fish harvesting project conducted in Lake George in 2015 removed 5 MT of TP in the form of fish biomass. So the predicted TP load increase from a free-flowing lower Ocklawaha, while not insignificant, is in the range of other permitted TP loads to the LSJR, and within the realm of reduction achieved by projects currently functioning elsewhere in the basin. Should FDEP choose to pursue this restoration, and if a mitigation were deemed appropriate to offset potential harm based on the predicted TP load increase, it would likely be achievable through a combination of treatment project options directed elsewhere in the middle St. Johns, Lake George, or the freshwater LSJR. This fact, combined with the understanding of other adverse impacts that occur as a result of reservoir drawdowns, a necessary management action for the maintenance of the reservoir, appears sufficient such that a recommendation of denial, on the grounds of the detrimental impacts to downstream water quality, is no longer a certainty for this restoration permit.
APPENDIX A—WATER BUDGET FOR THE LOWER OCKLAWAHA RESERVOIR REACH
Discharge statistics for this nutrient loading analysis were developed for the Rodman Reservoir reach of the Lower Ocklawaha River (LOR), and for the freshwater reach of the Lower St. Johns River (LSJR). A 20-year baseline period of record from October 1993–September 2013 of observed and simulated daily mean discharge were used in the analysis, as this corresponds to the available discharge record for the LSJR. The total reservoir reach inflow was calculated as the sum of the measured discharge data for Eureka (USGS #02240500, at County Highway 316, approximately 26 miles above the Ocklawaha Mouth), Orange Creek (USGS #02243000 on Hwy. 21 in Orange Springs), and Orange Springs (SJRWMD station #10362775), with simulated discharge used to estimate flow from ungauged areas. Outflow was calculated as Rodman Dam plus the volume exiting during boat lock-throughs at the Buckman Lock. One Buckman lock-through at a reservoir stage of 20’ is equivalent to 1.008 million cubic ft, or, 11.67 cubic feet/sec per day per lock-through, which is roughly equivalent to one percent of the dam mean daily discharge per lock-through. Lock-through discharge data are available from 1995 – 2004, with the subsequent time period estimated from recent reports from September 2009 to the present, which indicate a range of 34 to 72 lockages per month.
In his groundwater modeling analysis, Tibbals (1989) predicted that the impoundment of Rodman Reservoir elevated the regional Florida aquifer potentiometric surface by up to 2 ft, extending a distance of 10 – 15 miles, and increased regional artesian spring discharge by 14 ft3/s. If this is the case, then conversely, one might expect that removal of the reservoir would result in a reduction in the discharge of artesian springs in the region. Such a regional groundwater change would likely have some bearing on the free-flowing river effects on the LSJR, as it indicates that increased LOR flow (and load) would be compensated to some degree by artesian spring discharge reduction in other St. Johns River springs. Examination of the local upper Floridan monitoring well water level data during reservoir drawdowns suggests that changes in reservoir stage are communicated to the regional potentiometric surface through the changes in head pressure over the submerged springs. Abrupt reductions in the upper Floridan water level in the Forest Road No. 77 well, located adjacent and just to the south of the reservoir, can be seen coincident with reservoir drawdowns (Figure A-4). Delayed and less abrupt reductions in water level in the Frontier Dance Hall well, located 9.3 miles southeast of the reservoir are also discernible during reservoir drawdowns. Temporary reductions in artesian spring discharge are also apparent in the discharge time series for Silver Glen Springs, and in the intermittent discharge measurements made for Salt Springs and Croaker Hole. These transient changes in Florida Aquifer water level and artesian spring discharge could also occur from normal seasonal changes in aquifer recharge.
The relationship between reservoir stage, upper Floridan aquifer water level and artesian spring discharge are not well known as of this writing, and will need to be verified with additional data collection, analysis and groundwater modeling. For the purpose of this analysis, an operational presumption is followed such that any increases in discharge contributed by artesian springs submerged in Rodman Reservoir will be offset by decreases in artesian spring discharge elsewhere to the St. Johns River. As Rodman Reservoir submerged springs, based on limited sampling data, exhibit chemical constituent makeup similar to that of the St. Johns River springs group, the presumption in this analysis is that the reallocation of artesian spring would result in no net nutrient load change to the St. Johns. Hence, the submerged spring load is omitted from the free-flowing river load estimate. This presumption is incorporated in part because it imparts another conservative assumption into the analysis, as the omission of low concentration artesian spring flows increases downstream concentrations by omitting their dilution effect.
APPENDIX G — PROPOSED OCKLAWAHA RIVER RESTORATION NUTRIENT LOAD EFFECTS ASSESSMENT PLAN
In a draft revised restoration plan (FDEP, 2010), additional pre-construction phases have been proposed to moderate the transition of reservoir to river floodplain forest prior to construction, and to reduce the transient effects from oscillating wetting and drying cycles that accompany reservoir refills and storm-event related floodplain inundation and dewatering. This revised plan calls for successive reservoir drawdowns, separated by partial refills lasting for 18 to 20 months. The first drawdown to 11 feet would be initiated in October, with the first partial refill the following February to 16.5 ft This would be followed by another drawdown to 11 feet in 19 months, again to 11 feet, then a partial refill to 14.5 feet. A final drawdown would again be done in another 19 months to 9.5 feet, with the last refill to 11 feet. The restoration construction phase would begin after the stabilization at the 11 feet stage.
"Ocklawahaman" NOTE: I have emphasized in BOLD italics some of the above excerpted sentences and paragraphs of text from John Hendrickson's SJ2016-1 paper that in my opinion are extremely informative.