MINIMUM FLOWS AND LEVELS
RULE REVISIONS MATERIALS
1. Chapter 40D-2
a. Summary of Recommended Changes
b. Proposed 40D-2, Board Draft (Unchanged from August 19)
c. Water Use Permitting Basis of Review Changes (Revised from
2. Chapter 40D-4
a. Proposed 40D-4, Board Draft (Unchanged from August 19)
b. ERP Basis of Review Changes (Unchanged from August 19)
3. Chapter 40D-8
a. Summary of Recommended Changes
a. Proposed 40D-8, Board Draft (Revised from August 19)
0 printed on
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40D-2 CONSUMPTIVE USE OF WATER
CHANG RECOMMENDED TO AUG T GOVERNINGBQAR DRAFT
40D-2, F.A.C., Consumptive Use of Water:
Rewrite Basis of Review Section 4.3 to incorporate all provisions previously in 40D-8
regarding the effect of a Minimum Flow or Level on water use permits so that:
1. Where the actual water level is at or above the Minimum Flow or Level all
applications for permits (new or renewal) will be evaluated to ensure that
they do not cause the actual flow or level to fall below the Flow or Level.
2. Where the actual flow or level is below the Minimum Flow or Level:
a. Unless allowed by the applicable recovery strategy, no new
quantities permitted and the applicant must compete for water that
would otherwise be authorized under the recovery strategy.
b. Existing permits that cause the actual flow or level to be below the
Minimum Flow or Level are subject to a recovery strategy when
implemented by the District;
c. Until a recovery strategy is implemented by the District a Minimum
Flow or Level will have no permitting impact on existing, renewal or
d. When a recovery strategy is implemented in Northern Tampa Bay,
applicants and existing permittees must comply with the recovery
strategy, 40D-2 and the Basis of Review with the exception that
compliance with 40D-2.301(b) and (c) (wetland, lake, etc., impacts)
and Section 4.2 of the Basis of Review is not required as they
relate to existing impacts.
Chapter 40D-2 and Water Use Permitting Basis of Review
Changes Necessary to Implement Minimum Flows and Levels
RULES OF THE
SOUTHWEST FLORIDA WATER MANAGEMENT DISTRICT
CHAPTER 40D-2 CONSUMPTIVE USE OF WATER
40D-2.091 Publications Incorporated by Reference
40D-2.301 Conditions for Issuance of Permits
40D-2.091 Publications Incorporated by Reference
The "Basis of Review for Water Use Permit Applications" ___ Apri 1~+-994, the
"Agricultural Water Use Form," July 24, 1990, and the "Agricultural Water Allotment Form," July 24,
1990, are hereby incorporated by reference into this Chapter and are available from the District
Specific Authority 373.044, 373.113 FS. Law Implemented 373.219, 373.239, 373.243 FS. History -
New 10-1-89, Amended 11-15-90, 2-10-93, 3-30-93, 7-29-93, 4-11-94,
40D-2.301 Conditions for Issuance of Permits
(1) In order to obtain a Water Use Permit, an Applicant must demonstrate that the water use
is reasonable and beneficial, is in the public interest, and will not interfere with any existing legal use
of water, by providing reasonable assurances, on both an individual and a cumulative basis, that
the water use:
(a) Is necessary to fulfill a certain reasonable demand;
(b) Will not cause quantity or quality changes which adversely impact the water
resources, including both surface and ground waters;
(c) Will not cause adverse environmental impacts to wetlands, lakes, streams,
estuaries, fish and wildlife, or other natural resources;
(d) Will comply with the provisions of 4.3 of the Basis of Review described in 40D-
2.091 not cause water lve's or rates of flow to deviate from the ranges set forth in Chapter 40D--;
(e) Will utilize the lowest water quality the Applicant has the ability to use;
(f) Will not significantly induce saline water intrusion;
(g) Will not cause pollution of the aquifer;
(h) Will not adversely impact offsite land uses existing at the time of the application;
(i) Will not adversely impact an existing legal withdrawal;
(j) Will utilize local water resources to the greatest extent practicable;
(k) Will incorporate water conservation measures;
(I) Will incorporate reuse measures to the greatest extent practicable;
(m) Will not cause water to go to waste; and
(n) Will not otherwise be harmful to the water resources within the District.
(2) (3) No change.
Specific Authority 373.044, 373.113, 373.149, 373.171 FS. Law Implemented 373.219, 373.223,
373.229 FS. History Readopted 10-5-74, Amended 12-31-74, 2-6-78, 7-5-78, Formerly 16J-2.11,
16J-2.111, Amended 1-25-81, 10-1-89, 2-10-93,
DRAFT 2 -1
WATER USE PERMITTING BASIS OF REVIEW
4.0 CONDITIONS FOR ISSUANCE--TECHNICAL CRITERIA
4.3 MINIMUM FLOWS AND LEVELS
Applicants shall demonstrate compliance with established minimum flows and levels as set
forth in 40D-8 F.A.C. as follows:
1_. For water bodies where the actual flow or level is at or above a Minimum Flow
or Level, withdrawals shall not cause the actual flow or level to fall below the Minimum Flow
or Level on a Long-term average basis. "Long-term" means an evaluation period used in
assessing withdrawal impacts through modeling or statistical data analysis that represents
a period of time of sufficient length such that the evaluation period is insensitive to unstable
fluctuations of the variables utilized in the assessment .e.g.. changes in withdrawal rates, and
changes in hydrologic conditions, in order to simulate steady state conditions. This will vary
because professional judgement is necessary to establish the parameters to be used in the
assessment of each application depending on the geology and climate of the area of
withdrawal, the depth of and number of wells and the quantity to be withdrawn.
2. For water bodies where the actual flow or level is below the Minimum Flow or
Level and the District has implemented regulatory requirements as part of a recovery strategy
pursuant to Section 373.0421(2). F.S.. the following applies. When completed, the entire
recovery strategy will be contained within the District's Water Management Plan.
a. Unless otherwise provided for in the District's recovery strategy.
additional withdrawal quantities shall not be allowed and applications for new uses of water
must compete under Section 373.233. F. S. for a quantity of water that would otherwise be
authorized by the District under the recovery strategy.
b. Existing permits with withdrawals that cause or contribute to the existing
flow or level being below the Minimum Flow or Level will be subject to a recovery strategy as
described in 40D-8.031(4)(b) and Chapter 40D-2. F.A.C.
3_. Within the portions of Hillsborough County. Pasco County and Pinellas County
for which a recovery strategy has been implemented by the District, where a withdrawal
impacts a Minimum Flow or Level established in 40D-8.624 or 40D-8.626 and the actual level
at any of the impacted Minimum Flow or Level sites is below the Minimum Flow or Level.
applicants and existing permittees shall demonstrate compliance with all the requirements of
the recovery strategy adopted by rule and applicable to the affected water body. Chapter
40D-2. F.A.C. and this Basis of Review with the exception that compliance with 40D-
2.301(1)(b) and (c) and Section 4.2 of the Basis of Review is not required as they relate to
SEPTEMBER 8, 1997 BOARD DRAFT B4-1
4. With regard to existing permits and renewal and new withdrawal applicants.
where a withdrawal impacts a Minimum Flow or Level established in 40D-8.624 or 40D-8.626
and the actual level at any of the Minimum Flow or Level sites is below the Minimum Flow or
Level and the District has not yet implemented a recovery strategy pursuant to Section
373.0421(2). F.S.. the provisions of this Section 4.3 and 40D-2.301(1)(d) do not apply.
APter w th drawal must not cause:
TV VSIII VVILI II A l I .4VVQ4Ii II I W4% 1 01 %.-A %L !.4 1 .
42. 1--Stremflow to b .,ie reduced below the minimum regulatory flow level a.s
established in Chapter 40D 8, F.A.C.
regulatory leave! established in Chapter 40DW8, F.A.C.
m,, I,4SEPTEMBER 8, 1997 BOARD DRAFT B4-2,. I n .
1:094 slimam AliallNal iimical~ahmal n Clammiar A-l Q C: A f
*Chapter 40D-4 and Environmental Resource Permitting Basis of
Review Changes Necessary to Implement Minimum Flows and Levels
40D-4.091 Publications and Agreements Incorporated by
The following documents are hereby incorporated into this chapter and Chapters
40D-40 and 40D-400, F.A.C.:
(1) "Basis of Review for Environmental Resource Permit Applications within the
Southwest Florida Water Management District, ______wAp ri 7.99." This
document is available from the District upon request.
(2) (3) No change.
Specific Authority 120.54(8), 373.044, 373.046, 373.113, 373.171, 373.414 FS. Laws
- -I implemented 120.54(8), 373.046,- 373.103(8),.373.114, -373.403,. 373.413, 373.414,
373.416, 373.429, 373.441 FS. History New 4-2-87, Amended 3-1-88, 9-11-88, 10-1-88,
4-1-91, 11-16-92, 1-30-94, 10-3-95, 12-26-95, 5-26-96, 7-23-96, 4-17-97,
BASIS OF REVIEW AMENDMENTS
184.108.40.206 Water quantity impacts to wetlands and other surface waters
Pursuant to paragraph 3.1.1(a), an applicant must provide reasonable assurance
that the regulated activity will not change the hydroperiod of a wetland or other
surface water, so as to adversely affect wetland functions or other surface water
functions as follows:
(a) Whenever portions of a system, such as constructed basins, structures,
stormwater ponds, canals, and ditches, could have the effect of reducing the
depth, duration or frequency of inundation or saturation in a wetland or other
surface water, the applicant must perform an analysis of the drawdown in
water levels or diversion of water flows resulting from such activities and
provide reasonable assurance that these drawdowns or diversions will not
adversely impact the functions that wetlands and other surface waters
provide to fish and wildlife and listed species.
(b) Increasing the depth, duration, or frequency of inundation through changing
the rate or method of discharge of water to wetlands or other surface waters
or by impounding water in wetlands or other surface waters must also be
addressed to prevent adverse effects to functions that wetlands and other
surface waters provide to fish and wildlife and listed species. Different types
of wetlands respond differently to increased depth, duration, or frequency of
inundation. Therefore, the applicant must provide reasonable assurance that
activities that have the potential to increase discharge or water levels will not
adversely affect the functioning of the specific wetland or other surface water
subject to the increased discharge or water level.
DRAFT B 4-1
(c) Whenever portions of a system could have the effect of altering water levels
in wetlands or other surface waters, applicants shall be required to monitor
the wetland or other surface waters to demonstrate that such alteration has
not resulted in adverse impacts, or to calibrate the system to prevent adverse
impacts. Monitoring parameters, methods, schedules, and reporting
requirements shall be specified in permit conditions.
Id) The activity shall not reduce or suppress the flow of a watercourse or the
level of water in a wetland or other surface water below a minimum flow or
level that has been established pursuant to Section 373.042, F.S.
4.6 Overdrainage and water conservation Where practicable, .systems shall be
1. maintain water tables at the highest practicable level; the depth to which the
water table can be lowered will be determined based on the potential
adverse impact on recharge, the effect on water resources (quality and
quantity), and the necessity for fill and its impact on existing natural upland
-2. preserve site environmental values; and
3. not waste freshwater through overdrainage; and
4. not lower water tables which would adversely affect existing legal uses; and
5. preserve site groundwater recharge characteristics; and
6. retain water on-site for use and re-use for irrigation and other reasonable
4.6.1 In addition to the design considerations in 4.6 above, the system shall not reduce
or suppress the flow of a watercourse or the level of water in a wetland or other
surface water or the level of around water below a minimum flow or level that has
been established pursuant to Section 373.042. F.S.
DRAFT B 4- 2
40D-8 WATER LEVELS AND RATES OF FLOW
CHANGES RECOMMENDED TO AUGUST GOVERNING BOARQDJRA
40D-8, F.A.C., Water Levels and Rates of Flow:
1. Add that where actual flows and levels are below Minimum Flows and Levels the
District will implement a recovery strategy. See 40D-8.011(1)
2. Delete definitions for "Normal Pool", "Recovery Level" and "Water Resources" as
these terms are no longer used within Chapter 40D-8. See 40D-8.021.
3. Delete description of the basis and factors upon which a Minimum Flow or Level
is based due to the continued concern that the description is confusing and
possibly inconsistent with the provisions of 373.0421(1). Further it described
only one basis not all possible bases under Section 373.042 and 373.0421, F.S.
for setting Minimum Flows and Levels. See 40D-8.031
4. Transfer all provisions regarding the effect of a Minimum Flow or Level on water
use permits to Chapter 40D-2 since that is where water use applicants and staff
will look for criteria to be used in evaluating water use permit applications with
respect to their impact on a Minimum Flow or Level. See 40D-8.031 and now
see Section 4.3 of the Consumptive Use Permitting Basis of Review
5. Add provision that the manner in which Minimum Flows and Levels are
implemented in water use and environmental resource permitting are contained
in Chapters 40D-2 and 40D-4. See 40D-8.031(3)
6. Add that the City of Tampa may meet the required Minimum Flow for the
Hillsborough River by diverting flow from the Reservoir or Sulphur Springs. See
7. Add that the Minimum Flow for the River must be met beginning January 1, 1999
in order to allow time for the City of Tampa to install the necessary equipment.
8. Revise definition of Pre-modification Annual Low to more accurately describe
what it is. See 40D-8.603(3)(a)
9. Correct that references in other Chapters of the District rules to minimum level
refers to the adopted Minimum Level. See 40D-8.603(5)(c)
10. Add that the District will consider the Guidance Lake Levels and any Minimum
Lake Level in establishing a schedule for operations of District operated control
structures. See 40D-8.621(2)
11. Delete all provisions describing the scientific methodology used to establish the
Minimum Wetland, Lake and Aquifer Levels until it is known which Minimum
Level alternative the Governing Board selects as the methodology is different for
the various alternatives. See 40D-8.624 and 40D-8.626
12. Delete all proposed Minimum Wetland, Lake and Aquifer Levels until the
Governing Board determines which of the alternative Levels will be established
as the Minimum Levels.
13. Add "sunset" provision for the levels set in 40D-8.624(1) and 40D-8.626(4). This
provision requires the Minimum Levels to be re-evaluated, and readopted if
necessary, by July 1, 2007.
1 RULES OF THE
2 SOUTHWEST FLORIDA WATER MANAGEMENT DISTRICT
3 CHAPTER 40D-8
4 WATER LEVELS AND RATES OF FLOW
5 40D-8.011 Policy and Purpose
6 40D-8.021 Definitions
7 40D-8.031 Implementation
8 40D-8.041 Minimum Rftes-ef Flows e and Level
9 40D-8.603 GuidanceMA"na"eme Levels for Lakes and Oth.r Impoundmnts
10 40D-8.605-Cyclic Variations for Minimum Watcr Lcvcl
11 40D 8.611 Minimum Flood Levels
13 A40 8.616 -Posted Notic
14 40D-8.621 Operating Levels for Lakes and Other' I -mpoundmen with District-owned
15 Control Structures
16 40D-8.624 Sehedule-ef Levels for Lakes- and Wetlands, ,and Other ImpoundmWn
17 40D-8.626 Minimum Aquifer Levels in Northern Hillsborough. Pasco. and Pinellas
19 40D-8.011 Policy and Purpose.
20 (1) The purpose of Chapter 40D-8 is to establish Minimum Fflows and Levels
21 at specific locations throughout the District pursuant to Section 373.042 and 373.0421. F.
22 S.. to describe Guidance Levels for lakes, and to describe how the Minimum Flows and
23 Levels will be used by the District. In those areas where the actual flow or water level is
24 below the Minimum Flow or Level the District will implement a recovery strategy which will
25 be contained within the District's Water Management Plan and. if required by law. portions
26 or all may be adopted by rule.
27 (2) Where appropriate, Minimum flows and Lievels may reflect seasonal
28 variations and may include a schedule of variations and other measures appropriate for
29 the protection of non-consumptive uses andef the water resources.
30 (3) A further purpose of Chapter 40D-8 is to establish minimum flood levels and
31 warning levels for surface waters which are anticipated to occur on a somewhat regular
32 basis, and which shall serve as a precautionary warning to all persons who would propose
33 to construct facilities which may be damaged by periodic high water levels.
34 (4) Minimum Flows and Levels prescribed in Chapter 40D-8 are used as a basis
35 for imposing limitations on withdrawals of water and the design and construction of surface
36 water management systems. certain other activities. These limitations are prescribed in
37 this and other chapters pfrts of the rules of the District-- as specified in 40D-8.031(3).
39 Specific Authority 120.54, 373.016, 373.023, 373.044, 373.103 FS. Law Implemented
40 373.026, 373.042, 373.044. 373.086 FS. History New 6-7-78, Amended 1-22-79,
41 Formerly 16J-8.01, Amended
SEPTEMBER 8, 1997 BOARD DRAFT 8-1
1 40D-8.021 Definitions.
2 The terms set forth herein shall have the meanings ascribed to them unless the
3 context clearly indicates otherwise, and such meanings shall apply throughout all District
4 these rules. To facilitate easier reference, certain terms defined by applicable statute have
5 -been included verbatim with appropriate. citation. The terms defined in Rule 40D-1.102
6 40D-8-021 shall also apply throughout Chapter 40D-8.
7 (1) "Guidance Levels" Levels, determined by the District using the best
8 available information and expressed in feet relative to National Geodetic Vertical Datum.
9 used as advisory information, including for the District, lake shore residents and local
10 governments or to aid in the control of adjustable structures. For lakes for which levels
11 were adopted after September 8. 1997. Guidance Levels include: Ten Year Flood Warning
12 Level; Pre-modification Annual High Level: Post-modification Annual High Level: Pre-
13 modification Annual Low Level: and Post-modification Annual Low Level. For lakes for
14 which levels were adopted before September 8. 1997. Guidance Levels are the Ten Year
15 Flood Warning Level, the Annual Flood Level, the Low Level, and. if adopted for the lake.
16 the Extreme Low Level.
17 (2) "Long-term" An evaluation period used in assessing withdrawal impacts
18 through modeling or statistical data analysis that represents a period of time of sufficient
19 length such that the evaluation period is insensitive to unstable fluctuations of the variables
20 utilized in the assessment e.g.. changes in withdrawal rates, and hydrologic conditions, in
21 order to simulate steady state conditions. This will vary because professional judgement
22 is necessary to establish the parameters to be used in the assessment of each application
23 depending on the geology and climate of the area of withdrawal, the depth of and number
24 of wells and the quantity to be withdrawn.
25 (3) "Minimum Flow" means the level of flow for a surface watercourse at which
26 further withdrawals would be significantly harmful to the water resources or ecology of the
28 (1)-"Management rango" means the difference between the established
29 minimum watcr levels and minimum flood levels, an d reproIaIntai the capability of Ln
301 impoundment to rWece eive, carry, or store water, to preserve non-. consumptiv. uses of a
31 surface water body, and within this range the District applies and requires best surface
31 IIIl ,19r ,lll ll l LSee %A .,a lI VIWAI A I ll I LlI L. Ifl 0 L;O1%.0 JP6I V0L I III --164 POII I I.4111%,f IV I I.%AIP l
32 water management practices.
33 (4-) "Minimum water Ltevel" means the level of surface water, water table, or
34 potentiometric surface at which further withdrawals would be significantly harmful to the
35 water resources of the area. Such level shall be expressed as an elevation, in feet relative
36 to National Geodetic Vertical Datum.above men sea and may incorporate a low
37 management level and an extreme low management level, which together establish the
39 "tu l.... '""
40 (5) "Management range" means, for those lakes with levels adopted on or after
41 September 8. 1997. the difference between the applicable Annual Low Level and Annual
42 High Level pursuant to 40D-8.603. For lakes with levels adopted prior to September 8.
43 1997. management range means the difference between the Low Level, or Extreme Low
44 Level, if adopted for the lake. and the Annual Flood Level.
46 .shall b r.all..ow.d to fluctuate without interfe.Clre.nc, e....xcept a approved by the Board for theo,,..
SEPTEMBER 8, 1997 BOARD DRAFT 8-2
liLI I* VikA i .O P %J III LI Me Wk-ktW l ~d A LO I % oii. 4.1 1%.0 11 1 %A I I a I I av i%. I 1%.#V. 41 C i
7 availbJAle data
1o2a' (10ea) recurrng interAal Aor and roperqutiliateinc of sureacewxter. t Q n perce
1. %I WWI, -1 %i.0 .,1 ..........,*.JII 1- 01. I....1 %01-1,,-. 4:.I 1w ...., .-!, .O...W..1 %A ,,It .... IFMFrr
13 (b r tio n-, oafa dat, c.manage f promafl is ts oi ,enoasion, and mecsrsiv,
9 %1erat9ion, 6 aL maintBnan of structur1s or d.ev A %I rIqires Wl a l consideration PON.
16 Storage for aquifer recharge.
17 ------ (e)--Non consumptive uses, including but not limited to, navigation,
18 rWecreation, and aesthetics. A 81
20 Specific Authority i120i.54. 373.016, 373.023, 373.044, 373.103 FS. Law Implemented
21 373.016, 373.042, 373.044 FS. History New 6-7-78, Amended 1-22-79, Formerly 16J-
22 8.02. Amended
24 40D-8.031 Implementation.
25 (1) The provisions of Chapter 40D 8 of those rules shall continue to be
28 and Pinellas Anclote River Basins and shall be implemented immediately and shall apply
I i%29 within the area annexed into the District by Chapter 781% 165, Laws of Florida10.=, and shall
32 herein shall l 1l become effective immediately upon:i-.1 i
33 l1. I.Ins ltallavltion of a staff gauge in a prominent location on the waterI
34 beoed -
l36 -I3i.- Publication of notice in a newspaper having general circulation
0 Speific Authority 12.4, 3.016, 3.3,aagemet levelas0, .1 adjed b te clic variation
39 shall become effective when similar notice has been given.
40 (16) No Guidance management Lievels shall be prescribed for any reservoir or
21 other373.016, 373ificia structure which is located entirely within amends owned 1-22-79, or oterwsly 16J-e
42 controlled by the user, and which require water only for filling, replenishing, and
22 8.02, Amended
24 40D-8.031 Implementation.
45 filling, replenishing, and maintaining of the water level, and
3'0 "1&-IM-16 ... "....
SEPTEMBER 8, 1997 BOARD DRAFT 8-3
1 (b) That the Pre-modification or Post-modification Annual High. as
2 applicable minim-um flod -level ,pursant tc .s Ar40D 8.021 and 40 1 and the Ten
3 Year Eflood WwVaming Lievel. all as determined pursuant to the procedures set forth in the
4 District's Lake Level Methodology Manual incorporated by reference in Rule 40D-8.091
5 pursuant t Rul. s 40D 8.021 and 40D,-8.63 may be established for any lake eor the
6 itmpeAndment determined by the Board to be in the public interest.
7 (23) No Guidance management Lievels shall be prescribed for Lake Manatee in
8 Manatee County, Ward Lake in Manatee County, the City of Tampa Reservoir on the
9 Hillsborough River in Hillsborough County, and the Peace River/Manasota Regional Water
10 Supply Authority Reservoir General Devel.pment Utilities Reserv'ir c-nstructd in
11 conne.4 action with the Southwest Florida Water Managem4nt District's Permit Numbers
12 7500016, 74 172, ad 75 20 in DeSoto County.
13 (3 The manner in which the Minimum Flows and Levels established in this
14 Chapter 40D-8 are implemented in the District's consumptive use and environmental
15 resource permitting programs is described in rules 40D-2.301 and Section 4.3 of the Basis
16 of Review described in 40D-2.091. and Sections 220.127.116.11 and 4.6 of the Basis of Review
17 described in 40D-4.091.
18 (4) Where the actual flow or level of a water body is below the Minimum Flow or
20 (a Upon adoption, a Minimum Flow or Level shall have no regulatory
21 effect under Chapter 40D-2, F.A.C. unless and until the District has a recovery strategy.
22 pursuant to Section 373.0421(2). F.S. that addresses when and how established Minimum
23 Flows or Levels will affect existing permits issued under Chapter 40D-2. F.A.C. and
24 applications for permits under Chapter 40D-2. F.A.C.
25 (b Pursuant to 373.0421(2). F.S. the District shall expeditiously
26 implement a recovery strategy with the intent to achieve recovery to the established
27 Minimum Flow and Level as soon as practicable. The portion of the recovery strategy
28 containing criteria that must be met by permittees and applicants under Chapters 40D-2
29 and 40D-4 F.A.C. shall be adopted by rule. The entire recovery strategy shall be
30 contained in the District's applicable Regional Water Supply Plan for the area. and the
31 District's Water Management Plan.
32) The District shall annually review the status of the water levels for those
33 water bodies for which Minimum Flows or Levels have been established, and, where
34 appropriate, change the status reflected in the tables set forth in 40D-8.624 and 40D-
36 (6} Establishment of a Minimum Flow or Level shall not be deemed to be a
37 determination by the Governing Board that any quantity above the established Minimum
38 Flow or Level is available for allocation to consumptive uses. For example., the District
39 may by regulation or order reserve such quantities as it deems necessary pursuant to
40 Section 373.223(3). F.S.
42 Specific Authority 120.54. 373.016, 373.023, 373.044, 373.103 FS. Law Implemented
43 120.543. 373.016, 373.023, 373.042, 373.0421, 373.044, 373.086, 373.103 FS. History -
44 New 6-7-78, Amended 10-16-78, 1-22-79, Formerly 16J-8.03, Amended 3-23-81.
SEPTEMBER 8, 1997 BOARD DRAFT 8-4
1 40D-8.041 Minimum Rates-ef Flows e td-evel.
2 (1. Minimum Flows For the Lower Hillsborough River
3 al For the purposes of Minimum Flows the Lower Hillsborouah River is
4 defined as the river downstream of Fletcher Avenue. The Lower Hillsborouah River
5 includes Sulphur Springs, an artesian spring that enters the river via a short spring run
6 located 2.2 miles downstream of the Hillsborough River.
7 (b} The Minimum Flow for the Lower Hillsborough River at the base of the
8 City of Tampa's dam shall be ten (10) cubic feet per second (cfs) when the surface water
9 elevation at USGS gaae 02304500 is at or above 18.0 feet NGVD and 0 cfs when the
10 surface water elevation is below 18.0 feet NGVD. This Minimum Flow has been
11 determined based on the structural alterations in and along the River and the dependence
12 of viable ecological communities downstream of the dam with flows from the Hillsborouah
13 River Reservoir and Sulphur Springs. The City of Tampa may meet this flow requirement
14 by diverting flow from Sulphur Springs or the Reservoir. The required flows will become
15 effective January 1. 1999.
16 (c) The District will establish a Minimum Flow for Sulphur Springs in the
17 future. As part of that process the District will evaluate if additional flows from Sulphur
18 Springs are available to supplement the Minimum Flow for the Hillsborouah River at the
19 base of the City of Tampa's dam.
20 (2) Minimum Flows for the Tampa Bypass Canal
21 a The Tampa Bypass Canal extends 12 miles from above Fletcher
22 Avenue to McKay Bay. Structure 160 serves as the barrier between the freshwater and
23 tidal portions of the Tampa Bypass Canal.
24 bb The Minimum Flow for the Tampa Bypass Canal at Structure 160 is
25 0 cfs. This Minimum Flow accounts for the structural nature of the Canal, its operational
26 constraints and the relationship of ecological communities in the tidal reaches of the Canal
27 and McKay Bay with freshwater flows through Structure 160.
28 (c) The Minimum Flow for the Tampa Bypass Canal at Structure 160 is
29 established specific to the physical configuration and operations constraints of the Tampa
30 Bypass Canal as they exist at the time of adoption of this Minimum Flow. If physical
31 modifications to the Tampa Bypass Canal are made. the District shall reevaluate the
32 Minimum Flow at Structure 160.
34 Specific Authority 120.54. 373.044, 373.133, 373.149, 373.171 FS. Law Implemented
35 373.042, 373.086, 373.339 FS. History Readopted 10-5-74, Amended 12-31-74,
3 6 Formerly 16J-O. 15, 40D-1.601, Amended 10-1-84,
37 40D-8.091 Publications Incorporated By Reference
38 The determination of Guidance Flood Levels, including the Annual High and Low
39 Levels set forth in 40D-8.603 are more particularly described in the Lake Level
40 Methodology Manual, dated September. 1997 which is hereby incorporated into this
41 chapter. This document is available from the District upon request.
42 Specific Authority 120.54. 373.016. 373.023. 373.044. 373.103. 373.113. 373.133.
43 373.149. 373.171 FS. Law Implemented 120.54. 373.016. 373.023. 373.026. 373.0395.
SEPTEMBER 8, 1997 BOARD DRAFT 8-5
1 373.042. 373.0421. 373.044. 373.086. 373.103. 373.171. 373.339 FS. History New
3 40D-8.603 "Management Guidance Levels for Lakes en~ Other I.mp.oundmnt.-
4 (1) Guidance Levels adopted by the Governing Board on or after September 8.
5 1997 and the method for calculating those Levels are set forth in 40D-8.603(2) and
6 8.624(3) and (4). Guidance Levels adopted by the Governing Board prior to September
7 8. 1997 are listed in 40D-8.624(8).
8 (21 Flood and High Levels
9 (a The Ten (10) Year Flood Warning Level is provided as an advisory
10 guideline for lake shore development. The Ten (10) Year Flood Warning Level.
11 incorporates the level of flooding expected on a frequency of not less than the ten (10)
12 year recurring interval, or on a frequency of not greater than a ten percent (10%)
13 probability of occurrence in any given year. The Ten Year Flood Warning Level is
14 calculated as described in Chapter Two of the District's Lake Level Methodology Manual
15 described in 40D-8.091.
16 (b4 The Pre-modification Annual High Level for lakes is the highest level
17 to which a lake is expected to fluctuate on an average annual basis. The Pre-modification
18 Annual High Level is calculated as described in Chapter Three of the District's Lake Level
19 Methodology Manual described in 40D-8.091.
20 (~c The Post-modification Annual High Level, for lakes with hydroloaic
21 regimes modified by surface water conveyance systems or natural occurrences (e.g.
22 sinkholes) is the highest level to which a lake is expected to fluctuate on an average
23 annual basis. The Post-modification Annual High Level for lakes with an adjustable
24 structure is a peaking elevation and not one which is maintained. The Post-modification
25 Annual High Level is calculated as described in Chapter Four of the District's Lake Level
26 Methodology Manual described in 40D-8.091.
27 (3) Low Levels
28 (a) The Pre-modification Annual Low Level is the lowest level to which a
29 lake is expected to fluctuate on an average annual basis. The Pre-modification Annual
30 Low Level is calculated as described in Chapter Three of the District's Lake Level
31 Methodology Manual described in 40D-8.091.
32 (b) The Post-modification Annual Low Level, for lakes with hydrologic
33 regimes modified by anthropogenic activities excluding withdrawals or natural occurrences
34 (e.g. sinkholes) is the expected annual low level of a lake which has been influenced by
35 such activities and which no longer fully exhibits pre-modification fluctuations. The Post-
36 modification Annual Low Level may be used as a guide to operate a lake control structure.
37 for those lakes with control structures. The Pre-modification Annual Low Level is
38 calculated as described in Chapter Four of the District's Lake Level Methodology Manual
39 described in 40D-8.091.
40 (4. Posted Notice
41 (a) Staff gauges will be installed in prominent locations on each lake for
42 which Guidance Levels or Minimum Levels have been established. A notice shall be
43 posted in the immediate proximity of the staff gauge indicating that Levels have been
SEPTEMBER 8, 1997 BOARD DRAFT 8-6
1 (b) The notice shall indicate the elevations of the Guidance Level and the
2 established Minimum Level.
3 (5} Renaming of Levels
4 (a Lakes for which lake levels were adopted prior to September 8. 1997
5 had what were referred to in the District's Rules as management levels and alternatively
6 as minimum levels. These levels were the Ten Year Flood Warning Level, the Minimum
7 Flood Level, the Low Management Level and for some lakes there was a Extreme Low
8 Management Level. As of (effective date of these proposed rule revisions) these levels
9 are now referred to as the Guidance Levels. For those lakes with levels established prior
10 to September 8, 1997 the Minimum Flood is now named the Annual Flood Level, the Low
11 Management Level is now named the Low Level and the Extreme Low Management Level
12 is now named the Extreme Low Level.
13 () For lakes for which levels were adopted before September 8. 1997.
14 a reference within the District's rules to the applicable minimum level or to established
15 minimum water levels shall refer to the Low Management Level, or. if adopted for the lake.
16 the Extreme Low Management Level. Those lakes for which levels were adopted prior to
17 September 8. 1997 are set forth in 40D-8.624(3) along with the adopted levels.
18 (c) For lakes for which levels were adopted on or after September 8. 1997
19 a reference in the District's rules to the applicable minimum level or to established
20 minimum water levels shall refer to the adopted Minimum Level described in 40D-8.624(2).
21 () In establishing minimum watr levels, minimum flood lvels and othr
22 management levels for lakes and other impoundment, the Board shall use the best
23 information available
24 (2) Data from technical publications, topographic mop
25 Data Reports anad other studies and records may be considered.l.h Ifrmtion may AlCso b
26 .obtained from aeri6-' al mapping, hydrographs, bottom .contour mapping, stageduration
27 curves, water quality records, stratified bcach deposits, precipitation data and other
28 S ottes.
29 ---(3), Field investigation may be used to determine past surace levels from water
30 maCrs, wetland vegetation, and dry land vegetation, and to establish the elevation of septic
32 Specific Authority 373.016, 373.023, 373.044, 373.103 FS. Law Implemented 373.016,
33 373.042, 373.044 373.086 FS. History New 6-7-78, Formerly 16J-8.672. Paragraphs
34 (2)(h) and (i) Formerly 16J-8.6721. Paragraph(4) Formerly 16J-8.673. Amended
36 40D-8.605 Cyclic Variations for Minimum Water Level
38 impoundment shall bI lowered bIowII the low management level periodically to. -allowV
40 protection of non.consumptive uses. The lowered leave! is designated the extreme low
41 managementI level.
42 (2)-The low management level shall be the applicable minimum watcr leve! for
44 thc actual water level has failed to reode to the extreme low management lcvel; in which
SEPTEMBER 8,1997 BOARD DRAFT 8-7
1 eAvent the extreme lowI management level shall become the applicable minimum water level
2 for the lake or othor impoundment until the actual water level recedes to or below thc
3 extreme low management level. Whenever, the actual water l.vel recedes to or below th
4 extreme low managA ement level, th applicab e minimum water level for th lake or other
5 impoundment shall ;immediately be raised on; e again to thoC low managemeI...nt level andI =
6 the cyclic variations shall continue.
7 Specific Authority 373.016, 373.023, 373.044, 373.103 FS. Law Implemented 373.016,
8 373.042, 373.044. 373.086 FS. History New 6-7-78, Formerly 16J-8.671. Amended
10 40D-8.611 Minimum Flood Levels
11 1\) The minimum flood level ;%0%o1indicates the minimum level to which high water
12 Iemay b expected to rise on a s,.omew, t ~, lar., basis and will nLat neessarily correson
13 to any pa4icular flood frequency. Flood waters may often ris above the minimum flood
15 -(2) FDocks, a0Q walls, septic thanks, drain fields, floor slabs, and other physical
16 improvements, on land near lakes and other impoundments for which management levels
17 have been established, should be so located and constructed that their function will not be
19 (3) No st rulcture, improvement, or device shal lli be constructed or operated in
21 through the full management rangc established for such im poundment.
19 I.11d I", l r oil VVeII I II ,,, LUI I U I IIIA.I IlVVI l U IW 1 ILLI Io1f vo1 I%.,aUI
22 (4)-Propcrty owners are hereby advised that compliance with District Rules and
23 Regulations does not relieve owners of the responsibility of complying with other
24 regulations and ordinances required by local governing bodies, e.g., as in connection with
25 the National Flood Insurance Program.
26 Specific Authority 373.016, 373.023, 373.044, 373.103 FS. Law Implemented 373.016,
27 373.042, 373.044 FS. History New 6-7-78, Formerly 16J-8.672. Repealed
28 40D-8.613 Ten (10) Year Flood Warning Levels.
29 (l1)Vl IFlood warning levels are provided for a suIIace water body as an advliovy
31 are advised that flooding on a frequency of not lss than a tn (10) yar recurring interval
32 is expected to occur at th indicated elevation. Flood waters may often rise above the flood
35 improvements, on land near lakes and other impoundments for which flood warning levels
36 have been established, Ashould be o locatId and constructed siciently abov the flood
38 Specific Authority 373.016, 373.023, 373.044, 373.103 FS. Law Implemented 373.016,
39 373.042, 373.044 FS. History New 1-22-79, Formerly 16J-8.6721. Repealedmn
41 40D-8.616 Posted Notice.
39 373.042, 373.044 FS. History New 1-22-79, Formerly 16J-8.6721 Repealed
1 (1) 1,Staff gauges wil be installed in prominent locations on Iach lak or other
2 impoundment for which a management range has been established. A notice shall be
3 posted in the immediate proximity of the staff gauge indicating that management levels
4 have ben est abliHhed.
5 Mam(2 )--The notice shall indicate the elevations of the minimum flood level and the
6 applicable minimum water level.
7 Specific Authority 373.016, 373.023, 373.044, 373.103 FS. Law Implemented 373.016,
8 373.042, 373.044 FS. History New 6-7-78, Formerly 16J-8.673. Repealed
10 40D-8.621 Operating Levels for Lakes, and Other Impoundments with District
11 -owned Control Structures.
12 (1) Schedules, levels, and procedures for operation of lakes with a District-
13 owned control structure and other impoundment s equipped with structures shall be
14 established by the Board.
15 (2) The operating range for a structure of a lake or other impoundment shall be
16 prescribed as that between the high operating level and the low operating level.
17 (a) High operating level shall be established by the Board in consideration
18 of the Guidance Levels, public testimony and in keeping with the best lake control
19 management surface water management practices.
20 (b) Low operating level shall be established by the Board in consideration
21 of Guidance Levels, any applicable Minimum Level, public testimony and in keeping with
22 the best lake control management surface water management 4 practices.
23 } Best lake control management practices in the design, construction.
24 operation, and maintenance of structures or devices requires a consideration and
25 evaluation of both long-term and short-term effects of the activity upon the of the District.
26 Factors to be considered include the following:
27 (a) Conservation and proper utilization of surface water.
28 (b) Prevention of damage from floods, soil erosion, and excessive
30 (c) Preservation of natural resources, fish and wildlife,
31 (d) Storage for aquifer recharge.
32 (e) Non-consumptive uses, including but not limited to. navigation.
33 recreation, and aesthetics.
34 (.f Compliance with any Minimum Level established for the lake.
35 (43) A prescribed schedule for operation of all lakes and other impoundm.nts with
36 structures shall be established by the Board. The schedule will contain time sequences by
37 which the levels of the water body will be maintained throughout the established
38 management range. While recognizing the difficulty of maintaining precise control of actual
39 levels, the schedule shall provide the guideline by which the operator of the structure will
40 attempt to maintain the prescribed levels insofar as he has control.
41 Specific Authority 373.016, 373.023, 373.044, 373.103 FS. Law Implemented 373.016,
42 373.042, 373.044 FS. History New 6-7-78, Formerly 16J-8.677.
SEPTEMBER 8, 1997 BOARD DRAFT 8-9
1 40D-8.624 Sehedule-ef Levels for Lakes; and Wetlands --nd -ther
4 (1) Within Northern Hillsborough and Pasco Counties Minimum Levels have
5 been established on Lakes Barbara. Big Fish. Cypress. Dosson. Helen. Ellen. Little Moon.
6 Rainbow and Sunshine based on the Priority Schedule for the Establishment of Minimum
7 Flows and Levels within the District's Water Management Plan. dated March. 1995. as
8 updated June. 1996. The Minimum Levels established for these lakes shall be reevaluated
9 by the Governing Board no later than July 1. 2007. If changes are necessary, the
10 Governing Board shall reestablish the Minimum Levels and adopt new Minimum Levels to
11 replace those set forth in 40D-8.624(2) below for these lakes.
12 (2+) Levels for lakes and other imp undm% ns are hereby established as set forth
13 in the following table.feews- For those lakes whose Minimum Level elevation is followed
14 by an asterisk (*). it has been deemed that upon the effective date of the rule adopting the
15 Minimum Level for those lakes the lake level is below the Minimum Level. If insufficient
16 data exists to determine if the lake level is below the Minimum Level the lake level can be
17 determined to be below the Minimum Level based on a comparison with similar lakes by
18 use of aerial photographs and evaluation of biological indicators.
19 SEE SEPARATE HANDOUT FOR MINIMUM LAKE LEVELS
20 Location by County and Name of Ten Year Annual Annual Minimum
21 Basin Lake Flood High Low Level
Guidance Guidance Guidance (NGVD)
(NGVD) (NGVD) (NGVD)
22 (a) In Charlotte County
23 Within The Peace River
26 (b) In Citrus County
27 Within The Coastal
28.. Rivers Basin
30 (c) In Citrus County
3.1 Within The
32 Withlacoochee River
35 (d) In DeSoto County
36 Within The Peace River
SEPTEMBER 8, 1997 BOARD DRAFT 8-10
1 (e) In Hardee County
2 Within The Peace River
5. (f) In Hernando County
. Within The Coastal
7 Rivers Basin
. (a) In Hernando County
10. Within The
11 Hillsborough River
14 (h) In Hernando County
15 Within The
16 Withlacoochee River
19 (i) In Highlands County
20 Within The Peace River
23 (i) In Hillsborough
24 County Within The
25 Alafia River Basin
27 (k) In Hillsborough
28 County Within The
29. Hillsborough River
32 (I) In Hillsborough Sapphire 64.1 63.5 61.9
33 County, Within the Lake
34. Northwest Hillsborough S-14,T-
3.5 Basin 27,R-18
Cypress 49.5 48.9 47.3
SEPTEMBER 8, 1997 BOARD DRAFT 8-11
Dosson 55.1 53.4 50.0
Sunshine 55.1 52.8 50.6
Lake 54.2 53.0 51.4
27. R-1 8
Lake Ellen 54.2 53.0 51.4
Lake 54.2 53.0 51.4
Little Moon 40.8 39.0 37.1
1 (m) In Lake County
2 Within The Green
3 Swamp Basin
5. (n) In Levy County
7 Withlacoochee River
ip (o) In Manatee County
11 Within The Manasota
SEPTEMBER 8, 1997 BOARD DRAFT 8-12
1 (p) In Marion County
2 Within The
3. Withlacoochee River
S (a) In Pasco County Big Fish 77.4 76.5 74.6
7 Within the Coastal Lake
8 Rivers Basin S-21.T-
24 R-1 9
9 (r) In Pasco County
10 Within The Green
11 Swamp Basin
13 (s) In Pasco County
1 Within The
15 Hillsborough River
18 (t) In Pasco County
12 Within The Pinellas-
20 Anclote River Basin
22 (u) In Pasco County
23 Within The
24 Withlacoochee River
21 (v) In Pinellas County
32 Within The Pinellas- River
Anclote River Basin
31. (w) In Polk County
36 Within The Green
37 Swamp Basin
SEPTEMBER 8, 1997 BOARD DRAFT 8-13
1 (y) In Polk County
2 Within The
a Hillsborouah River
.6 (z) In Polk County
7_ Within The Peace River
10 (aa) In Sarasota
11 County Within The
12 Manasota Basin
14 (bb) In Sumter County
15 Within The Green
16 Swamp Basin
18 (cc) In Sumter County
19 Within The
20 Withlacoochee River
23 (3 Guidance Levels established for lakes prior to September 8. 1997 are set
24 forth in the following table:
25 TABLE OF LAKE LEVELS PREVIOUSLY ADOPTED HAVE BEEN OMITTED FOR
26 THIS DRAFT BECAUSE THE ONLY CHANGE IS TO THE NAME OF THE LEVELS AS
27 DESCRIBED IN 40D-8.603(5) NOT TO THE LEVELS THEMSELVES.
28 Specific Authority 373.044, 373.113, 373.171 FS. Law Implemented 373.016, 373.042,
2 9 373.103 FS. History New 6-7-78, Amended 1-22-79, 4-27-80, 10-21-80, 12-22-80, 3-23-
30 81, 4-14-81, 6-4-81, 10-15-81, 11-23-81, 1-5-82, 3-11-82, 5-10-82, 7-4-82, 9-2-82, 11-8-
31 82, 1-10-83, 4-3-83, 7-5-83, 9-5-83, 10-16-83, 12-12-83, 5-8-84, 7-8-84, 12-16-84, 2-7-85,
32 5-13-85, 6-26-85, 11-3-85, 3-5-86, 6-16-86, Formerly 16J-8.678, Amended 9-7-86, 2-12-
33 87, 9-2-87, 2-18-88, 6-27-88, 2-22-89, 3-23-89, 9-26-89, 7-26-90, 10-30-90, 3-3-91, 9-30-
34 91, 10-7-91, 7-26-92, 3-1-93, 5-11-94, 6-6-96, 2-23-97.
35 40D-8.626 Minimum Aquifer Levels in Northern Hillsborough. Pasco. and Pinellas
37 1 The Minimum Aquifer Level shall be a Long-term average water level and
38 shall be used as a Long-term average when evaluating water use permit applications.
SEPTEMBER 8,1997 BOARD DRAFT 8-14
1 (21 The aquifer sites for which Minimum Aquifer Levels have been established
2 as set forth in 40D-8.626(4) below were selected using the following guidelines:
3 (a) the site is located in an area that is or may be experiencing adverse
4 withdrawal impacts:
5 () the site has a Floridan monitor well
6 (c) sites where a surficial well is co-located with the Floridan well (well
7 nests) are preferred:
8 (d wells or well nests having a long period of record are preferred:, and
9 ideally include data before water withdrawals commenced: and
10 ) the well or well nest should be within close proximity of lakes or
12 (3 Aquifer levels are deemed to be below the Minimum Aquifer Level when the
13 six-year-average level is below the Minimum Aquifer Level. If insufficient data exists to
14 determine if the aquifer level is below the Minimum Aquifer Level set forth in 40D-8.626(4)
15 the aquifer level can be determined to be below the Minimum Aquifer Level based on an
16 evaluation of regional aquifer level data. including potentiometric surface maps. For those
17 aquifer sites whose Minimum Aquifer Level elevation is followed by an asterisk (*), it has
18 been deemed that upon the effective date of the rule adopting the Minimum Level for those
19 aquifer sites the aquifer level is below the Minimum Aquifer Level as described in 40D-
20 8.626(4) below.
21 (4 Minimum Aquifer Levels shall be established as follows. These Minimum
22 Aquifer Levels shall be reevaluated by the Governing Board no later than July 1. 2007. If
23 changes are necessary, the Governing Board shall reestablish the Minimum Aquifer Levels
24 and adopt new Minimum Aquifer Levels to replace those set forth below.
25 SEE SEPARATE HANDOUT FOR MINIMUM AQUIFER LEVELS
26 Well Latitude Longitude Minimum Level
27 Name (NGVD)
28 (a) T-1 280708 820748
29 (b) T-2 280510 820438
30 (c) T-3 280849 820537
31 (d) CB3ED 282221 822419
32 (e) TMR1D 281719 822246
33 (f) TMR3D 281745 822342
34 (g) DMW500 281204 822238
35 (h) MW2-1000 281019 822114
36 (i) HILLSB 13 280703 823027
37 (j) CALM 33A 280834 823435
SEPTEMBER 8, 1997 BOARD DRAFT 8-15
1 (k)JAMES11 280653 823415
2 (I) COSME3 280608 823529
3 (m) EW 2N 281011 823905
4 (n) EW11 280905 823905
5 (o) EW N4 280945 .823804
6 (p)MATTS 281102 822924
7 (q)SP42 281036 823056
8 (r) Debuel 280741 822709
9 (s) Lutz Park 280913 822832
10 (t) RMP8D1 280342 823256
11 (u) Hutchinson 280552 823257
12 (v) Eagles CC 280609 823830
13 (w) Lutz Lake 280921 822230
15 (x) Ledantec 281255 823103
16 (y) Starkey 281312 823616
18 (z) Starkey 1A 281443 823401
20 (aa) Starkey 281454 823802
22 (bb) MW1 281447 823542
23 (cc) Seven 281223 823933
24 Springs Deep
25 (dd) Starkey 281135 823607
26 Ranch WRAP
27 (ee) NPMW-7 281825 823405
28 (ff) NPMW-11 281631 823411
29 (gg) SR52 282010 823737
31 (hh) TMR4D 281650 822444
SEPTEMBER 8, 1997 BOARD DRAFT 8-16
1 (ii) SR52 East 281918 822645
2 (jj)CB1SED 282100 822628
3 (kk) FK6D 281938 822423
4 (II) Morris 280652 822042
5 Bridge 1
6 (mm) Morris 280656 821751
7 Bridge 13
8 (nn) DGW2 280827 822055
9 (oo) Bexley 281149 823017
10 (pp)SERW 282206 822711
11 (qq) SRW 282035 822839
12 (rr) TMR-2 281845 822240
13 (ss) Pasco 13 281559 822645
14 (tt) SR54 281144 823046
15 (uu) Berger 280700 822942
16 (vv) B-1 282259 822824
18 Specific Authority 120.54. 373.042. 373.044. 373.113. 373.171 FS. Law Implemented
19 120.54. 373.016. 373.023. 373.0395. 373.042. 373.171 FS. History New
SEPTEMBER 8, 1997 BOARD DRAFT 8-17
1 Lake Level Methodology Manual
3 CHAPTER ONE INTRODUCTION
4 1.1 Objectives Under Part I of Chapter 373, Florida Statutes (FS) and Chapter 40D-8,
5 Florida Administrative Code (FAC), the District is responsible for establishing
6 minimum levels for lakes within its jurisdiction. Pursuant to Chapter 373.042, FS,
7 minimum levels shall be calculated using best available information, and may reflect
8 seasonal variations. The District shall also consider, and at their discretion may
9 provide for, the protection of non-consumptive uses in establishment of Minimum
10 Levels. The objective of this document is to identify and describe the usual
11 procedures and methods used by District staff in determining and proposing lake
12 levels to the Governing Board.
13 1.2 History of the Lake Levels Program Since the mid-1970's, the District has
14 maintained a program to adopt management levels for lakes throughout the District.
15 These management levels were selected to be representative of a healthy
16 fluctuation range for each lake and can be used for water management purposes.
17 Prior to 1996, management levels had been set on 397 lakes. However, in 1996,
18 revisions to Chapter 373, Florida Statutes resulted in changes to the Lake Levels
19 Program. The most substantial change to the program was the requirement that a
20 Minimum Level be established. This Minimum Level is the level of a lake at which
21 further withdrawals would be significantly harmful to the water resources of the
22 area. As a result of the 1997 rule revisions, for those lakes for which levels are
23 adopted after September 8, 1997, the terms management levels, Minimum Flood
24 Level and Low Management Level were changed to Guidance Levels, Annual High
25 Level and Annual Low Level, respectively. The Extreme Low Level was deleted
26 from the methodology and will no longer be an adopted level.
27 1.3 Criteria for Inclusion of Lakes in the Lake Levels Program Historically, lakes
28 were included in the Lake Levels Program based on several criteria. These criteria
29 included lakes with District water control structures, lakes with water use permits
30 and lakes 20 acres or larger with multiple owners. In response to legislative
31 mandates in 1996, criteria were added to the lake selection process which
32 emphasized lakes located in Water Resource Caution Areas, lakes in the vicinity of
33 major water withdrawals and lakes specifically identified by local governments or
34 other entities. The revisions to Chapter 373, F.S. also required that the District
35 adopt a Minimum Flows and Levels (MF/L) Priority List. The MF/L Priority List,
36 which identifies the lakes and the time frames for establishing levels, is included
37 in the District Water Management Plan.
38 1.4 Levels Established under the Lake Levels Program -The levels defined below
39 will be established based on the procedures and methods discussed in this
1 document. All levels shall be expressed in feet relative to National Geodetic Vertical
2 Datum (NGVD) of 1929.
3 Guidance Levels, as described in section 1.4. below, are established for all lakes
4 in the Lake Level program as follows. Pre-modification Guidance levels will be
5 determined for all lakes included in the Lake Levels Program. For lakes with
6 modified surface conveyance systems, Post-modification Guidance levels also will
7 be determined. The levels finally recommended to the Governing Board will depend
8 on the type of lake system.
9 A Minimum Level will also be determined and recommended to the Governing
10 Board for lakes included in the Lake Level Program.
11 1.4.1 Guidance Levels determined by the District using the best available
12 information and expressed in feet relative to National Geodetic Vertical
13 Datum. They are used as advisory information to aid in the control of
14 adjustable structures, for lake shore residents and for local governments.
15 Guidance Levels include: Ten Year Flood Warning Level; Pre-modification
16 Annual High Level; Post-modification Annual High Level; Pre-modification
17 Annual Low Level; and Post-modification Annual Low Level.
18 18.104.22.168 Ten (10) Year Flood Warning Level is an advisory level provided
19 as a discretionary guideline for lakeshore development. The Ten (10) Year
20 Flood Warning Level, incorporates the level of flooding expected on a
21 frequency of not greater than ten percent (10%) probability of occurrence in
22 any given year.
23 22.214.171.124 Pre-modification Levels refer to lake water regimes before
24 impacts by withdrawals and before modification of surface water conveyance
25 systems and water withdrawals.
26 126.96.36.199.1 Pre-modification Annual High Level the highest level to
27 which a lake is expected to fluctuate on an average annual basis.
28 188.8.131.52.2 Pre-modification Annual Low Level the lowest level to
29 which a lake is expected to fluctuate on an average annual basis.
30 184.108.40.206 Post-modification Levels refer to lake water regimes resulting
31 from alterations to the lake's surface water conveyance systems.
32 220.127.116.11.1 Post-modification Annual High Level Is for lakes with
33 water regimes resulting from alterations to the lake's surface water
34 conveyance systems. The Post-modification Annual High Level is the
35 highest level to which a lake is expected to fluctuate on an average
36 annual basis.
1 18.104.22.168.2 Post-modification Annual Low Level Is for lakes with
2 water regimes resulting from alterations to the lake's surface water
3 conveyance systems. The Post-modification Annual Low Level is the
4 lowest level to which the lake is expected to fluctuate on an average
5 annual basis.
6 1.5 Definitions The definitions in this section apply to the determination of all levels
7 described in this document.
8 1.5.1 P10 a percentile ranking defined as the elevation of the water surface of a
9 lake that is equaled or exceeded 10 percent of the time as determined from
10 a stage duration analysis.
11 1.5.2 P50 a percentile ranking defined as the elevation of the water surface of a
12 lake that is equaled or exceeded 50 percent of the time as determined from
13 a stage duration analysis.
14 1.5.3 P90 a percentile ranking defined as the elevation of the water surface of a
15 lake that is equaled or exceeded 90 percent of the time as determined from
16 a stage duration analysis.
17 1.5.4 Reference Lake Water Regime (RLWR) is a regional factor that
18 approximates the typical annual range of lake level fluctuations for lakes
19 within a similar hydrogeologic setting. The RLWR corresponds to the
20 difference between the Annual High and Annual Low Levels. It is used to
21 estimate the Annual High or Annual Low Level for lakes without hydrologic
22 data and biological indicators of one of the levels. (See Chapter Five.)
23 1.5.5 Stage Duration Curve a graphic representation of the percent of time the
24 water surface of a lake equals or exceeds a particular elevation. A stage
25 duration curve is developed by plotting lake level elevations against the
26 cumulative frequency of occurrence of those elevations for uniform
27 increments of time e.g., monthly readings.
28 22.214.171.124 Pre-modification Stage Duration Curve a stage duration curve
29 prepared using a minimum of six years of Pre-modification hydrologic data.
30 126.96.36.199 Post-modification Stage Duration Curve a stage duration curve
31 prepared using a minimum of six years of Post-modification hydrologic data
32 which begins after the construction/installation of surface water conveyance
34 1.5.6 Pre-modification a period before lake water regimes were impacted by
35 human activities such as alteration of surface water conveyance systems
36 and water withdrawals.
1 1.5.7 Post-modification a period after lake water regimes were impacted by
2 human activities, specifically alterations to the surface water conveyance
4 CHAPTER TWO DETERMINATION OF 10 YEAR FLOOD WARNING LEVELS
5 2.1 General The Ten (10) Year Flood Warning Level shall be established using
6 methods that correspond to the hydrology and type of conveyance system of the
7 lake being evaluated. Generally, lakes are classified as open basin lakes that
8 discharge and closed basin lakes. Open basin lakes that discharge are those lakes
9 that have a surface water conveyance system that by itself, or in series with other
10 lakes, connects to or is part of an ordered stream or creek. A closed basin lake,
11 has no outlet conveyance system, or has an outlet system that overflows only
12 during peak elevations. The methodology to be used for the determination of the
13 10-year Flood Warning Level of these two lake types is given below.
14 2.2 Lakes that discharge 10 Year Flood Warning Levels for lakes that discharge
15 shall be established using numerical single storm event models. Rainfall depths
16 shall be taken from Part D of the Environmental Resources Permitting Information
17 Manual (SWFWMD, 1996). Runoff volumes shall be computed using conventional
18 methods such as the Soil Conservation Service (SCS) curve number method, or
19 with standard infiltration formulas (e.g. Hortons Equation, Green-Ampt Equation).
20 Runoff distributions shall be computed using conventional methods including the
21 SCS method or other unit hydrograph methods, or the kinematic wave overland flow
22 method. Modeling programs that account for tailwater and compute backflow are
23 preferred for the hydraulic routing. The initial water level elevation used in the
24 model of a lake with no significant alterations to its natural surface conveyance
25 and/or outlet configuration shall be the Pre-modification Annual High Level as
26 defined in Chapter 3. The initial water level elevation of a lake with significant
27 alterations to its natural surface conveyance and/or outlet configuration shall be the
28 Post-modification Annual High Level as defined in Chapter 4. Exceptions shall be
29 based on peer review by the appropriate District staff and their consensus and
30 thoroughly documented in a report or memorandum to the project file.
31 2.3 Closed Basin Lakes 10-Year Flood Warning Levels for closed basin lakes and
32 lakes that overflow only during peak elevations shall be derived using a frequency
33 analysis of lake stage readings, or lake stages predicted by a physically based
34 numerical "continuous simulation model", or an empirical simulation model derived
35 either by linear or non-linear regression methods. The choice to use a linear or
36 non-linear regression technique shall be based on engineering judgement. The
37 simulation periods for either numerical or empirical models shall be based on not
38 less than thirty years of contiguous rainfall record. A composite of more than one
39 rainfall station in the region in which the subject lake is located is acceptable.
40 Calibration of the simulation model shall be based on as many indicators as
41 possible including, but not limited to, stage records and biological ans physical
42 indicators referenced in other parts of this document. If stage records do not exist
1 or the record does not contain peak elevation readings, then particular attention
2 should be given to obtaining eye-witness accounts of peak stages. Model
3 simulations to determine the 10-Year Flood Warning Level shall exclude effects of
4 water withdrawals.
1 CHAPTER THREE DETERMINATION OF PRE-MODIFICATION LEVELS
2 3.1 General Pre-modification Levels refer to lake water regimes prior to impacts by
3 human activities including modification of surface water conveyance systems and
4 water withdrawals.
5 3.1.1 Determination of Levels Pre-modification levels may be determined from
6 one or a combination of the following procedures more fully described in 3.2 and 3.3
7 below: analysis of stage duration data; and analysis of biological and physical water
8 level indicators. Other information used to determine Pre-modification Levels may
9 include, but not be limited to, survey data, maps and hydrologic data from such
10 sources as the United States Geological Survey, the Army Corps of Engineers and
11 General Land Office Notes. For lakes without stage duration data and biological
12 indicators, the Pre-modification Annual Low Level may be determined using the
13 Reference Lake Water Regime described in Chapter 5.
14 3.1.2 Reconciliation If Pre-modification Levels are determined using more than
15 one procedure, the Pre-modification Levels finally recommended will be a
16 reconciliation of the procedures used. Reconciliation involves comparing the levels
17 determined by the various methods. If the Pre-modification Levels determined by
18 each of the methods are similar, then the levels determined from analysis of stage
19 duration data take precedence unless the stage duration data are determined to be
20 impacted by water withdrawals. If the levels determined by each of the methods are
21 not similar, then possible reasons for the difference should be investigated.
22 Physical indicators should only be used to determine the Pre-modification levels if
23 biological indicators and hydrologic data are not available for the lake.
24 Biological and physical indicators have been used to determine water levels.
25 (Cooke, 1939; Davis, 1973; Florida Board of Conservation, 1969; Holcomb &
26 Wegener, 1971; Kenner, 1961). This approach has been used primarily to
27 determine high-water levels on lakes (Bishop, 1967; Knochenmus, 1967). Dooris
28 and Courser (1976) related both high and low water levels to various biological,
29 hydrological and cultural features.
30 3.2 Analysis of Stage Duration Data This method applies only to lakes which have
31 a minimum six years of Pre-modification stage data.
32 3.2.1 Pre-modification Annual High Level The Flood Annual High Level is
33 equal to the elevation corresponding to the P10 value on a Pre-modification
34 Stage Duration Curve.
35 3.2.2 Pre-modification Annual Low Level The Pre-modification Annual Low
36 Level is equal to the elevation corresponding to the P90 value on a Pre-
37 modification Stage Duration Curve.
1 3.3 Analysis of Biological and Physical Indicators This method is applied to lakes
2 for which one or more biological and/or physical indicators are present. The
3 methodology is based on known relationships between the location of wetland and
4 upland plant species and Pre-modification water levels.
5 3.3.1 Methods for Site Selection and Measuring Indicator Elevations -
6 Elevations of the indicators described in 3.3.2 shall be measured using
7 accepted surveying practices.
8 Locations for measuring biological indicators shall be chosen based on the
9 presence of the indicator plant species. Preferred locations will have
10 naturally vegetated wetlands around the lake, fringed by palmettos or other
11 upland plant species. As many transects as practical should be measured
12 in each of these areas. If multiple specimens of each indicator species occur
13 on the lake, then elevations should be determined for as many specimens
14 as practical.
15 In the absence of naturally vegetated wetlands and uplands, elevations shall
16 be measured for any available biological indicators included in this
17 document. Activities which may have impacted elevations, such as, filling,
18 soil subsidence, land clearing and similar activities shall be considered and
19 accounted for during evaluation and analysis of the data. If no biological or
20 physical indicators are present, proceed to Chapters Four and Five.
21 3.3.2 Pre-modification Annual High Level Biological indicators of the Pre-
22 modification Annual High Level may include, but not be limited to, the
23 following: palmetto (Serenoa repens); cypress (Taxodium sp.); longleaf pine
24 (Pinus palustrus); live oak (Quercus virginiana); and mature wax myrtle
25 (Myrica cerifera); lichens.
26 The method for measuring elevations of the indicator plants is described
27 below. Data recorded includes the elevation of the indicator species and for
28 trees, the diameter at breast height (DBH).
29 a. The elevation of the soil at the base of the lowest lakeward extent of
30 the palmetto (Serenoa repens) fringe is measured at the lowest
31 rooted extent of the plant.
32 b. The elevation of the soil at the base of the highest landward extent of
33 the cypress (Taxodium sp.) fringe is measured on the landward side
34 of the tree at the base of the trunk.
35 c. The elevation of the soil at the base of the lowest lakeward extent of
36 longleaf pine (Pinus palustrus) fringe is measured on the lakeward
37 side of the tree at the base of the trunk. Note: Only longleaf pine shall
38 be used to establish the Annual High Level.
39 d. The elevation of the soil at the base of the lowest lakeward extent of
40 the live oak (Quercus virginiana) fringe is measured on the lakeward
* 1 side of the tree at the base of the trunk for trees with a minimum
2 diameter at breast height (DBH) of 24".
3 e. The elevation of the soil at the base of the lowest lakeward extent of
4 the mature wax myrtle (Myrica cerifera) fringe is measured on the
5 lakeward side of the tree at the base of the trunk.
6 If more than one specimen of each indicator species is measured, then the
7 average elevation and standard deviation are calculated for the indicator
8 species. The average elevations of the indicator species are used in the
9 analysis of the Pre-modification Levels. If multiple biological indicators occur
10 on the lake, then the Pre-modification Annual High Level may be determined
11 from the biological indicators using best scientific judgement. If more than
12 one indicator plant species is present and measured, then typically the
13 priority order for use of biological indicators is palmetto, cypress, pine and/or
14 live oak and mature wax myrtle.
15 In the absence of, or in support of, biological indicators, physical indicators
16 may be used to determine the Pre-modification Annual High Level. Physical
17 indicators may include, but not be limited to, one or a combination, of the
19 a. The elevation of the toe of the highest landward scarp line. (Bishop,
2 0 1967 and Knochenmus, 1967).
21 b. Analysis of historic aerial photography, topographic maps, surveys,
22 site plans or other information that may identify locations or elevations
23 of biological indicators of the Pre-modification Annual Level.
24 c. The elevation of stratified beach deposits (Bishop, 1967 and
25 Knochenmus, 1967).
26 If none of the above biological or physical indicators exist along the lake
27 shore and cultivated groves of perennial woody species (i.e. citrus trees,
28 pine plantations) occur along the shoreline, then the lowest lakeward
29 elevation of the cultivated species may be used to determine the Pre-
30 modification Annual High Level. The lowest lakeward elevation of the crop
31 shall be measured at the lowest rooted extent of the crop. This method is
32 not applicable if the cultivated species is water dependent or water tolerant
34 3.3.3 Pre-modification Annual Low Level Biological indicators of the Pre-
35 modification Annual Low Level may include, but not be limited to, the
3 6 average elevation of the soil at the base of the lowest lakeward extent of the
37 cypress (Taxodium sp.) fringe. The elevation of the lowest lakeward extent
38 of the cypress trees shall be measured on the lakeward side of the tree at
39 the base of the trunk.
1 If other biological indicators of the Pre-modification Annual Low Level are
2 proposed, they must integrate water levels over a long period of time and
3 must persist after water levels have receded. For example, due to their rapid
4 growth and colonization rates, the lowest lakeward extent of emergent and
5 floating aquatic plants such as lotus (Nelumbo spp.), pickerel weed
6 (Pontederia spp.), maidencane (Panicum hemitomon) and torpedo grass
7 (Panicum repens) are not a suitable indicator of Pre-modification Annual Low
9 3.4 Reference Lake Water Regime The RLWR is used only if stage duration data
10 and biological or physical indicators of the Pre-modification Annual High or Annual
11 Low Level are not available. The Reference Lake Water Regime (RLWR)
12 represents a lake level fluctuation range, and therefore cannot be used alone to
13 establish lake levels. The RLWR is used to calculate a Pre-modification Annual
14 High or Annual Low Level once a Pre-modification Annual High Level or Annual Low
15 Level has been determined from one or more of the biological and physical
16 methods described above.
17 3.4.1 The Pre-modification Annual High Level is equal to the Pre-modification
18 Annual Low Level plus the RLWR.
19 3.4.2 The Pre-modification Annual Low Level is equal to the Pre-modification
20 Annual High Level minus the RLWR.
1 CHAPTER FOUR DETERMINATION OF POST-MODIFICATION LEVELS
2 4.1 General Post-modification Levels refer to lake water regimes impacted by human
3 activities, excluding water withdrawals. Post-modification levels may be determined
4 from analysis of stage duration data and analysis of modifications of the surface
5 water conveyance systems from the lake. Typically, biological indicators may not
6 be used to establish Post-modification levels. For lakes without stage duration data,
7 Post-modification levels may be determined by the application of the RLWR
8 described in Chapter 5.
9 If Post-modification levels are determined by more than one procedure, the Post-
10 modification levels finally recommended are a reconciliation of the procedures used.
11 Levels determined using analysis of stage duration data take precedence over the
12 levels determined from analysis of outfall elevations and the RLWR unless the
13 stage duration data is determined to be impacted by water withdrawals. Analysis
14 of outfall elevations and application of the RLWR is used only if sufficient stage
15 duration data are not available or if the lake is impacted by water withdrawals.
16 4.2 Analysis of Stage Duration Data This method applies only to those lakes with
17 a minimum of six continuous years of Post-modification stage duration data that
18 have not been impacted by water withdrawals.
19 4.2.1 Post-modification Annual High Level The Post-modification Annual High
20 Level is equal to the elevation corresponding to the P10 value on the Post-
21 modification Stage Duration Curve.
22 4.2.2 Post-modification Annual Low Level The Post-modification Annual Low
23 Level is equal to the elevation corresponding to the P90 value on the Post-
24 modification Stage Duration Curve.
25 4.3 Analysis of Outfall Elevations and Application of RLWR This method is
26 applied to lakes with modified surface water conveyance systems with less than six
27 continuous years of Post-modification stage duration data or lakes with stage data
28 impacted by water withdrawals. The method accounts for modifications to surface
29 water conveyance systems on the lake that does not allow water levels to be
30 maintained above the invert elevation of the outfall.
31 Elevations of outfalls will be measured using accepted survey practices. In the case
32 of open ditches or canals, bottom elevations shall be measured and the highest
33 legally existing and maintained stable point along the outlet profile shall be the
34 control point. For culverts or pipes, the invert (lowest point) of the pipe or culvert
35 shall be measured and this will be the control point. For fixed crest weirs, the
36 elevation of the top of the weir shall be measured and this shall be the control point.
1 Elevations will be established for all outfalls on the lake using the above
2 procedures. If there is more than one outfall on the lake, then the lowest outfall will
3 be considered as the control point.
4 4.3.1 Post-modification Annual High Level, Non-adjustable structure/open
5 conveyance The Post-modification Annual High Level is equal to the
6 elevation of the lowest legal flow line control. The lowest legal flow line
7 control is the highest stable point along the outlet profile.
8 4.3.2 Post-modification Annual Low Level, Non-adjustable structurelopen
9 conveyance The Post-modification Annual Low Level for lakes with less
10 than six continuous years of stage data or lakes with stage data impacted by
11 water withdrawals must be determined using the RLWR described in
12 Chapter 5. The Post-modification Annual Low Level is equal to the Post-
13 modification Annual High Level minus the RLWR.
14 4.3.3 Post-modification Annual High Level, Adjustable Structure The Post-
15 modification Annual High Level is equal to the highest elevation to which the
16 structure can be operated.
17 4.3.4 Post-modification Annual Low Level, Adjustable Structure The Post-
18 modification Annual Low Level is equal to the lowest elevation to which the
19 structure can be operated.
1 CHAPTER FIVE REFERENCE LAKE WATER REGIME
2 5.1 General In some cases there are little or no lake stage data or the existing lake
3 stage data reflects impacts due to human activities (e.g., water withdrawals). For
4 lakes which have sustained long-term water level declines, the P10 and P90 values
5 are generally uncorrelated to Pre-modification biological and physical indicators of
6 water levels. For the case where declines were caused by water withdrawals, the
7 P10 and P90 values can not be used to determine Guidance Levels because they
8 would grandfather effects of the water withdrawals into the adopted levels.
9 The Reference Lake Water Regime (RLWR) was developed to approximate the
10 annual range of lake level fluctuation that typically occurs and corresponds to the
11 range of fluctuation defined by the Annual High and Annual Low Guidance Levels.
12 The RLWR is a regional factor developed for lakes in the same hydrogeologic
13 region as the lakes for which levels are being established. It is applied to lakes with
14 less than six (6) years of stage data or where stage data have been significantly
15 influenced by water withdrawals. The District will continue to investigate methods
16 for calculating the RLWR and to estimate fluctuation ranges which can be used to
17 establish Guidance Levels.
18 Guidance Levels established by use of the RLWR are considered to be provisional
19 until six (6) years of lake stage data have been collected. Following collection of
20 sufficient data, an analysis of the adopted levels and stage data will be conducted
21 and a recommendation made as to whether the Governing Board should consider
22 re-establishing the levels.
23 In many areas of the SWFWMD thbre are few lakes that are unaffected by human
24 activities. To ensure that the RLWR is based on a representative number of lakes,
25 lakes that are in decline or that have experienced a decline in water levels, are
26 incorporated into the calculation of the RLWR. Though water withdrawals can
27 cause increases in annual lake water level fluctuations, long-term water level
28 declines are the cumulative result of these increases and typically do not occur in
29 a single year. Annual fluctuations in lake levels are still highly related to changes
30 in rainfall. In some instances lakes have experienced changes in annual
31 fluctuations of about 1 foot when comparing changes for different decades (e.g.
32 Horse Lake). A review of the data indicates that large annual fluctuations typically
33 occur in years of high rainfall following a period of low lake stage.
34 5.2 Calculation of RLWR Calculation and application of the RLWR is described in the
35 following sections. The District will continue to investigate methods for calculating
36 the RLWR and to estimate fluctuation ranges which can be used to establish
37 Guidance Levels.
38 5.2.1 CASE 1: Closed basin lake with less than six (6) years of stage data
1 The RLWR is calculated from lakes in the same hydrogeologic region as the lakes)
2 for which levels are being established. Following identification of representative
3 lakes in the region, the lake stage data are reviewed and lakes with less than six (6)
4 years of data are removed from the analysis. Annual stage duration curves are
5 prepared for each of the remaining lakes and differences between the annual P10
6 and P90 levels are calculated. Next, for each lake the median of the annual
7 differences is obtained to establish a median range of fluctuation for the respective
8 lakes. The RLWR is finally calculated as the median of the individual lake medians.
9 5.2.2 Case 2 Lake without data connected to lake with data
10 If a lake for which levels are to be established is connected via a surface water
11 conveyance system to a lake with data, then the RLWR shall be calculated using
12 data from the adjacent lake. The criteria for applying this method are: the lakes
13 must share the same level pool; and the lake must have a minimum of six
14 continuous years of stage data. For example: Lakes Rainbow and Little Moon are
15 connected above 34.67', NGVD and Rainbow Lake has stage data from 1972 to
16 1996. Therefore, the RLWR used for Little Moon Lake is equal to the median of the
17 differences between annual P10 and annual P90 values for Rainbow Lake.
18 5.2.3 CASE 3: Lake impacted by water withdrawals
19 For lakes affected by water withdrawals and that have less than six (6) years of
20 stage data prior to the initiation of withdrawals a site specific RLWR is calculated.
21 The site specific RLWR is calculated using data collected for the lake of interest.
22 Annual stage duration curves are prepared and differences between the annual P10
23 and P90 levels are calculated. The RLWR is calculated as the median of the
24 annual differences to establish a median range of fluctuation for the lake.
25 5.3 Application of RLWR The RLWR may be used to calculate either Pre-
26 modification Flood Levels or Low Levels depending upon the biological and
27 physical indicators present. The RLWR may also be used to calculate the Post-
28 modification Low Level.
29 5.3.1 Determination of Pre-modification Levels Using the RLWR
30 188.8.131.52 Pre-modification Annual Low Level If there are biological or
31 physical indicators of the Pre-modification Annual High Level then the Pre-
32 modification Annual Low Level can be calculated by subtracting the RLWR
33 from the Pre-modification Annual High Level elevation established by the
34 biological and/or physical indicators.
35 Pre-modification Annual Low Level = Pre-modification Annual High Level -
1 184.108.40.206 Pre-modification Annual High Level If there are no unimpacted
2 biological or physical indicators of the Pre-modification Annual High Level,
3 but there are biological indicators of the Annual Low Level, then the Pre-
4 Modification Annual High Level can be calculated by adding the RLWR to the
5 Pre-modification Annual Low Level elevation established by the biological
7 Pre-modification Annual High Level = Pre-modification Annual Low Level +
9 5.3.2 Post-modification Annual Low Level If the natural surface water
10 conveyance of a lake has been modified by construction of ditches or the
11 installation of culverts and there are no Post-modification data available, then
12 the Post-modification Annual Low Level must be determined from the
13 RLWR. In this case, the Annual Post-modification Low Level is determined
14 by subtracting the RLWR from the Post-modification Annual High Level
15 elevation established by analysis of outfall elevations.
16 Post-modification Annual Low Level = Post-modification Annual High Level -
18 Note: To use the RLWR either the Annual High Level or Annual Low Level must be
19 available as starting points.
20 5.4 Determining Effects of Water Withdrawals Before using period of record data
21 to establish Guidance Levels, it is necessary to determine whether the lake has
22 been or is potentially affected by water withdrawals. If lake levels are influenced by
23 water withdrawals, using the period of record data to establish Guidance Levels
24 may "grandfather" the effects of water withdrawals. Determining effects of water
25 withdrawals on lake levels can be accomplished using one or a combination of the
26 following methods:
27 Analysis of the hydrologic budget of the lake
28 Statistical regression analysis
29 Continuous simulation models
30 Groundwater flow models
31 Analysis of hydrographs
32 Analysis of existing studies
1 CHAPTER SIX ADDITIONAL INFORMATION SUPPLIED TO THE GOVERNING
2 BOARD FOR ADOPTING LAKE LEVELS
3 6.1 General District staff may provide additional information to the Governing Board
4 when recommending Guidance and Minimum Levels to the Governing Board. This
5 information may include, but not be limited to, bathymetric maps, aerial
6 photographs, and elevations of docks, seawalls, house slabs and other structures.
7 Information regarding typical uses of the lake (i.e., recreational uses, irrigation,
8 potable water supply) and surrounding land uses also may be provided.
2 Bishop, E.W. 1967. Florida Lakes. Part 1, A study of the high water lines of some Florida
3 lakes. Division of Water Resources, Florida Board of Conservation. Tallahassee,
5 Cooke, C.W. 1939. Scenery of Florida: Interpreted by a geologist. Florida Geological
6 Survey. Tallahassee, FL.
7 Davis, Jr., J.H. 1973. Establishment of mean high water lines in Florida Lakes.
8 Publication #24. Florida Water Resources Research Center. Gainesville, FL.
9 Dooris, P.M. and Courser, W.D. 1976. Determining stages and fluctuation schedules for
10 lakes in Central and South Florida. Florida Scientist. 39(1):14-18.
11 Florida Board of Conservation. 1969. Florida Lakes, Part III. Gazetteer. Division of
12 Water Resources. Tallahassee, FL.
13 Holcomb, D. and W. Wegener. 1971. Hydrophytic changes related to lake fluctuation
14 measured by point transects. Proceedings of the Twenty-fifth Annual Conference
15 of Southeastern Association of Game and Fish Commissioners. Charleston, SC.
16 Kenner, W.E. 1961. Stage characteristics of Florida lakes, Informational Circular #31.
17 Florida Geological Survey. Tallahassee, FL.
18 Knochenmus, Darwin D. 1967. Shoreline features as indicators of high lake levels. U.S.
19 Geological Survey Professional Paper 575-C.
20 SWFWMD. 1996. Environmental Resources Permitting Information Manual. Southwest
21 Florida Water Management Districts. Brooksville, FL