The proposed minimum flows for the upper Peace River are focused on returning perennial conditions to the upper Peace River. Specifically, they are based on maintaining the higher of the water elevations needed for fish passage (0.6 feet or 7.2 inches) or the lowest wetted perimeter inflection point (as much streambed coverage as possible for the least amount of flow). This approach yielded minimum low flows of 17 cfs (10.2 mgd), 27 cfs (16.2 mgd) and 45 cfs (27 mgd) at the Bartow, Fort Meade and Zolfo Springs USGS stream gages, respectively (Figure 3-1). These flows are required to be exceeded at least 95 percent of the time on an annual basis, which is nearly 350 days per year.
The District recognizes that multiple minimum flows are necessary to maintain the flow regime and health of aquatic ecosystems. At this time, however, only minimum low flows are being established. Mid- and high- minimum flows will be established once the
controlling factors that affect the mid and high flows are better understood. A detailed explanation of the development of these proposed flows can be found in the District’s publication titled “Upper Peace River: An Analysis of Minimum Flows and Levels” (August 2002), which is available from the District upon request. Wetted perimeter inflection points (Figures 3-6 and 3-7) and fish passage depths (Figure 3-8) were evaluated jointly to establish minimum flows for the low end of the flow regime of the upper Peace River. There was no assumption that fish passage needs will be met by the wetted perimeter approach. Rather, both approaches were used in tandem to evaluate the low minimum flow requirement, and the higher flow of the two was used as a conservative means for establishing the low minimum flow.
For rule development purposes, flows will be established at the Bartow, Fort Meade and Zolfo Springs USGS gage sites. These sites are also where the river flows will be monitored. However, a goal of the upper Peace River Recovery Strategy is to not only achieve these minimum low flows at these individual sites, but to achieve similar flow conditions
throughout the upper Peace River to attain the resource benefits of these flows (e.g., wetted perimeter, fish passage).
Compliance with the upper Peace River minimum flows is achieved when the actual river flows are at or above the established minimum flows for three consecutive years. Once the minimum low flow has been achieved and is followed by two years where the minimum low flow is not met within a rolling 10-year period (commencing with the three consecutive years of achievement), then the actual flow shall be considered below the minimum low flow. A determination of whether actual flows are meeting the established minimum flows is made at each one of the established minimums (Bartow, Fort Meade and Zolfo Springs).
From 1976 to 2000, the annual 95 percent exceedance flow met or exceeded the proposed minimum flow in 7 out of 25 years at the USGS Bartow Gage. From 1976 to 2000, the annual 95 percent exceedance flow met or exceeded the proposed minimum flow in 1 out of 25 years at the USGS Fort Meade gage. From 1976 to 2000, the annual 95 percent
exceedance flow met or exceeded the minimum flow in 22 out of 25 years at the USGS Zolfo Springs gage.
Peer Review of the Upper Peace River Minimum Flows
The District engaged the services of independent consultants in the field of stream and wetland ecology and hydrology to evaluate and review the data, methodologies and models supporting the development of minimum river flows. Two nationally recognized stream ecologists, Drs. Clifford Dahm (University of New Mexico) and James Gore (Columbia State University), and one wetland ecologist, Dr. Charles Klimas (independent consultant) served on the panel. Dr. Gore served as panel chairman. The scope of this voluntary review required the panel members to review the District’s publication titled: “Upper Peace River: An Analysis of Minimum Flows and Levels,” that outlines methods used in the development of minimum flows and levels for the upper Peace River. The panelists were asked to address the following specific tasks: (1) determine whether the method(s) used for establishing the minimum flows is scientifically reasonable; (2) if not scientifically reasonable, describe deficiencies, remedies or alternative approaches as appropriate; or (3) if reasonable, but an alternative is preferable, the panel should describe the method(s) with a qualitative
assessment of the effort required to implement the alternative method(s).
In their report titled “A Review of Upper Peace River: An Analysis of Minimum Flows and Levels” (November 2002), which is included as Appendix 2, the peer review panel
concluded that the “scientific analyses used to establish these recommended flows and levels are adequately described within the report and scientifically justifiable. Consideration of channel flow characteristics under these minimum discharge recommendations would be an additional factor worth evaluating, since support of both macroinvertebrate and vertebrate populations have been linked to these conditions (Statzner et al. 1988, Heade and Rinne 1990). The recommended minimum flows and water levels in this report, however, are based upon good hydrologic data, a well-established modeling protocol, and detailed measurements of channel habitat at multiple locations. We concur that the recommended minimum flows and levels represent thorough scientific analyses of good quality, historic and present data sets, and the recommendations are scientifically defensible and justifiable to meet the stated management objectives.” The peer review panelists made several
recommendations and suggestions regarding additional work that could be performed in the future. They encouraged the District to take an adaptive management approach in
developing minimum flows and levels and to “view the establishment of MFLs and rehabilitation goals as a dynamic process that results in improved flow criteria as new data and techniques are acquired.”
Bartow Gage-17 cfs
Fort Meade Gage-27 cfs
Zolfo Springs-45 cfs
Wetted Perimeter
Wetted Perim eter- USGS 453 & SWFWM D 150 - Flow s <100cfs
0 20 40 60 80 100 120 0 50 100 150 200 250
Wetted Perimeter (feet)
D isch ar g e ( cf s) A. B. Inflection point = 10 cfs Figure 3-5.
Map showing location of USGS gage sites with corresponding minimum low flow.
Figure 3-6.
Wetted perimeter is defined as the distance along the streambed and banks at a cross section where there is contact with water.
By plotting the response of wetted perimeter to incremental changes in discharge, an inflection can be identified in the resulting curve where small decreases in flow result in increasingly greater decreases in wetted perimeter.
0 5 10 15 20 25 30 35 40 45 50 Flow (cfs)
Wetted Perimeter
Bartow Ft Meade Zolfo Springs
26 cfs 26 cfs 17 cfs 0 10 20 30 40 50 60 70 80 Flow ( c fs )
Fish Passage (0.6 ft)
Bartow Ft Meade Zolfo Springs
27 cfs
45 cfs
16 cfs
Figure 3-7.
Flow needed at each transect site on the upper Peace River to wet the lowest wetted
perimeter inflection point (LWPIP). Superimposed on this plot are recommended LWPIP minimum flows.
Figure 3-8.
Flow needed at each transect site on the upper Peace River to allow a maximum depth of 0.6 foot for fish passage. Superimposed on this plot are
recommended minimum fish passage flows for three river segments.
Minimum Flows and Levels
Proposed Minimum and Guidance Ridge Lake Levels
Minimum levels are proposed for eight lakes in the Ridge area: Lakes Clinch, Eagle, McLeod and Wales (a.k.a. Wailes) in Polk County, and Lakes Letta, Lotela, Jackson and Little Lake Jackson in Highlands County (Figure 3-9). All eight lakes are designated “Category 3” lakes, i.e., lakes that do not have contiguous cypress-dominated wetlands. Minimum levels for Category 3 lakes are developed based on potential change in a number of parameters including: (1) lake mixing and susceptibility to sediment re-suspension, (2) water depth associated with docks, (3) basin connectivity, (4) species richness, (5) coverage of herbaceous wetland vegetation, (6) coverage of aquatic macrophytes, and (7) non-consumptive uses. Two minimum levels are proposed for each of these lakes: (1) a “minimum lake level” will be established at an elevation that the lake surface must equal or exceed 50 percent of the time, and (2) a “high minimum lake level” that the lake surface must equal or exceed 10 percent of the time. Three guidance levels, which serve as advisory information for lakeshore residents and local governments and can aid in the management or control of adjustable structures, are also proposed. These include a “10-year flood guidance level,” a “high guidance level” and a “low guidance level.”
The 10-year flood guidance level identifies the elevation that the lake surface may be expected to equal or exceed at a recurrence frequency of not less than 10 years and which may be expected to occur with a 10 percent probability in any given year. The high guidance level is the expected elevation that was historically exceeded 10 percent of the time. The historic period refers to a time when there were no measurable impacts due to withdrawals and structural alterations were similar to current conditions. Structural alterations are man’s physical alteration of the control point of a lake or wetland that affects water levels. The high guidance level is provided as an advisory guideline for the construction of lakeshore development, water-dependent structures and operation of water management structures. The low guidance level is the expected lake level that is exceeded 90 percent of the time based on a historic period. As with the high guidance level, the low guidance level is provided as advisory guideline for construction of water-dependent structures, information for lakeshore residents and operation of water management structures.
The minimum and high minimum lake levels for these lakes are based on levels determined to be necessary to meet the following parameters, unless other public health, safety or welfare, or adverse environmental impact considerations override these parameters: (1) lake mixing and susceptibility to sediment re-suspension, (2) water depth associated with docks, (3) basin connectivity, (4) species richness, (5) coverage of herbaceous wetland vegetation, (6) coverage of aquatic macrophytes, and (7) non-consumptive uses. When establishing minimum levels, changes and structural alterations to watersheds and surface waters (e.g., lake outlet structures, roads and buildings) are also considered.
There are two exceptions to the establishment of the minimum levels described above. Where the minimum lake level would result in a level higher than the “Historic P50,” the Historic P50 will be the minimum lake level. The Historic P50 is the percentile ranking represented by the elevation of the water surface of a lake or a wetland that is equaled or exceeded 50 percent of the time as determined from a long-term stage frequency analysis for
a historic period. Where the high minimum lake level is adjusted downward to prevent other public health, safety or welfare concerns or adverse environmental impacts, the minimum lake level will be adjusted downward to maintain a fluctuation regime similar to the natural regime.
Guidance levels for Category 3 lakes are determined using standard engineering approaches, analysis of lake stage records, indicators of historic water levels, elevations of existing water control structures and expected regional stage fluctuation ranges. A detailed discussion of procedures used to develop minimum and guidance levels for Category 3 lakes is provided in “A Multiple-Parameter Approach for Establishing Minimum Levels for Category 3 Lakes of the Southwest Florida Water Management District, June 14, 2001 Draft,” which is available upon request from the District.
Proposed minimum and guidance levels for the eight Ridge lakes in Polk and Highlands counties are listed in Table 3-2 and shown graphically in Figures 3-10 through 3-17. A detailed account of the development of the proposed levels is available in “Proposed
Minimum and Guidance Levels for Lakes Clinch, Eagle, McLeod and Wales in Polk County, Florida and Lakes Jackson, Little Lake Jackson, Letta and Lotela in Highlands County, Florida,” which is available upon request from the District.
Table 3-2.
Proposed Minimum and Guidance Lake Levels (Values listed are elevations in feet above the National Geodetic Vertical Datum of 1929)
Lake High Minimum Lake Level Minimum Lake Level 10-Year Flood Guidance Level High Guidance Level Low Guidance Level Lake Clinch 105.5 104.4 107.4 105.5 103.1 Eagle Lake 129.0 127.9 131.3 129.6 127.2 Lake McLeod 129.4 128.3 133.3 129.4 127.0 Lake Wales 107.7 106.6 114.1 ND ND Lake Jackson 102.4 101.3 104.1 102.6 100.2 Lake Letta 99.5 98.4 100.5 99.5 97.1 Lake Lotela 106.8 105.7 108.5 107.5 105.0 Little Lake Jackson 102.4 101.3 104.1 102.6 100.2 ND = Not Developed
Compliance with the proposed minimum levels will be achieved when the long-term P50 is at or above the minimum lake level and the long-term P10 is at or above the high minimum lake level. Long-term, as defined in 40D-8.021(7), FAC, means an evaluation period utilized to establish minimum flows and levels, to determine compliance with established minimum levels and to assess withdrawal impacts on established minimum flows and levels that represents a period which spans the range of hydrologic conditions that can be expected to occur based upon historical records, ranging from high water levels to low water levels. In the context of a predictive model simulation, a long-term simulation will be insensitive to
temporal fluctuations in withdrawal rates and hydrologic conditions, so as to simulate steady- state average conditions. In the context of an average water level, the average will be based upon the historic expected range and frequency of levels. Relative to minimum flow
establishment and minimum level establishment and compliance, where there are six years or more of competent data, a minimum of a six-year evaluation period will be used, but the available data and reasonable scientific judgment will dictate whether a longer period is used. Where there are less than six years of competent data, the period used will be dictated by the available data and a determination, based on reasonable scientific judgment, that the period is sufficiently representative of long-term conditions.
As of late 2005, seven of the eight lakes for which minimum levels are proposed are
currently staged above the proposed high minimum lake levels (Figures 3-10 through 3-17). The only exception is Lake Letta, where the water surface is currently between the proposed high minimum and minimum lake levels. However, based on 10-year periods for
establishing long-term stage percentile elevations, the proposed minimum levels have been met for five consecutive years at only one of the lakes — Eagle Lake in Polk County. Water levels at the remaining seven lakes have not equaled the proposed minimum levels for at least one of the past two years.
Peer Review
For Category 3 lakes, the peer review process involved determination of the scientific reasonableness of the proposed methodologies; evaluation of deficiencies; development of suggestions for alternative approaches; interaction with District staff, the general public and other stakeholders at a public meeting; preparation of a written report on review findings; and presentation of review findings to the District Governing Board. Reviewers included two eminent limnologists: Dr. Ken Wagner and Dr. Forrest Dierberg.
In their final report titled “A Review of A Multiple-Parameter Approach for Establishing Minimum Levels for Category 3 Lakes of the Southwest Florida Water Management
District,” which is included as Appendix 3, the reviewers note that the District’s proposal to consider a wide variety of parameters for development of minimum lake levels encompasses “the goals advanced by the current Water Resource Implementation Rule for protecting Florida’s water resources and environmental values while considering natural seasonal fluctuations in water levels.” Furthermore, they note “that the approaches taken by the District to determine minimum levels represent appropriate starting points for further methodological development and provide a sound basis for interim management.” The reviewers found “no major significant deficiencies in the manner in which data were collected or applied” and offered a variety of suggestions for modifying or supplementing the District’s proposed approach. The District has and will continue to explore the
reviewers’ suggestions and is committed to an adaptive management approach that will lead to the best possible minimum lake levels. As an example, the reviewers suggested that the Historic P50 elevation should be used for establishing the minimum lake level in cases where the elevation associated with one or more of the parameters used for levels development (e.g., basin connectivity) occur at an elevation greater than the Historic P50. This
recommendation has been incorporated into the approach used to develop the proposed lake levels.
N S W E N S W E Polk Highlands Eagle
Lake LakeMcLeod
Lake Wales Lake Clinch Lake Letta Lake Lotela Little Lake Jackson Lake Jackson District Boundary 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 1940 1950 1960 1970 1980 1990 2000 2010 W a ter E levati o n (ft ab o ve N G V D )
Dock-Use Std Aesth Std Basin Conn Std Sp Rich Std Mixing Std Rec/Ski Std
MLL 10-YR HGL, HMLL LGL Lake Clinch 77.0 ft 74.3 ft 105 110 115 120 125 130 135 1960 1970 1980 1990 2000 2010 W a ter E levati o n (ft ab o ve N G V D )
Dock-Use Std Basin Conn Std Aesth Std
Sp Rich Std Mixing Std Rec/Ski Std
HMLL MLL 10-YR HGL LGL Eagle Lake Figure 3-9. Location of eight Category 3 lakes with proposed minimum levels in Polk and Highlands counties.
Figure 3-10.
Mean monthly surface water elevations through October 31, 2003, and proposed guidance and minimum levels for Lake Clinch in Polk County. Proposed levels include the 10-year flood guidance level (10-YR), high guidance level (HGL), low guidance level (LGL), high minimum lake level (HMLL), and minimum lake level (MLL).
Figure 3-11.
Mean monthly surface water elevations through October 31, 2003, and proposed guidance and minimum levels for Eagle Lake in Polk County. Proposed levels include the 10-year flood guidance level (10-YR), high guidance level (HGL), low guidance level (LGL), high minimum lake level (HMLL), and minimum lake level (MLL).
105 110 115 120 125 130 135 1960 1970 1980 1990 2000 2010 W a ter E levati o n (ft ab o ve N G V D )
Dock-Use Std Aesth Std Sp Rich Std Basin Conn Std Rec/Ski Std Mixing Std
MLL LGL 10-YR HGL, HMLL Lake McLeod 85 90 95 100 105 110 115 120 1950 1960 1970 1980 1990 2000 2010 W ater E levati o n (ft ab o ve N G V D )
Rec/Ski Std Basin Conn Std Mixing Std
HMLL MLL 10-YR Lake Wales 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 1940 1950 1960 1970 1980 1990 2000 2010 Water E levati o n (ft ab o ve N G V D )
Dock-Use Std Basin Conn Std Aesth Std Mixing Std Sp Rich Std Rec/Ski Std
MLL 10-YR HGL LGL Lake Jackson 82.3 ft HMLLL Figure 3-12.
Mean monthly surface water elevations through October 31, 2003, and proposed guidance and minimum levels for Lake McLeod in Polk County. Proposed levels include the 10-year flood guidance level (10-YR), high guidance level (HGL), low guidance level (LGL), high minimum lake level (HMLL), and minimum lake level (MLL).
Figure 3-13.
Mean monthly surface water elevations through October 31, 2003, and proposed guidance and minimum levels for Lake Wales in Polk County. Proposed levels include the 10-year flood guidance level (10-YR), high minimum lake level (HMLL), and minimum lake level (MLL).