To amend Rule 40D-8.041, F.A.C. to establish minimum flows and levels for the upper Myakka River pursuant to Section 373.042, Florida Statutes (F.S.).

 

WATER MANAGEMENT DISTRICTS

Southwest Florida Water Management District

RULE NO.: RULE TITLE:

40D-8.041 Minimum Flows

PURPOSE AND EFFECT: To amend Rule 40D-8.041, F.A.C. to establish minimum flows and levels for the upper Myakka River pursuant to Section 373.042, Florida Statutes (F.S.).

SUMMARY: The District has identified seasonal low, medium and high flow periods for the Myakka River. Short-term minimum flow compliance standards were developed for each of these periods using a “building block” approach. For the Myakka River, historic flows demonstrate that a Minimum Flow for the low flow period greater than 0 cubic feet per second (cfs) is inappropriate due to the historically ephemeral nature of the system. Therefore, the Minimum Low Flow for the low flow period (Block 1, April 20 through June 25) is the natural flow minus 15% at the Sarasota USGS Gage. For the Minimum High Flow for the high flow period (Block 3, June 26 through October 26), is a stepped flow reduction of 16% and 7% of the historic flows, with the step occurring at the 15% exceedance flow (577 cfs) at the Sarasota USGS Gage. For the medium flow period (October 27 to April 19) it was determined that changes in habitat availability for fish and macroinvertebrates determined the Minimum Medium Flow. The Minimum Medium Flow is established as the flow less 5% at the Sarasota USGS Gage. Five and ten year means and medians are proposed as long-term compliance standards.

SUMMARY OF STATEMENT OF ESTIMATED REGULATORY COSTS: No Statement of Estimated Regulatory Cost was prepared.

Any person who wishes to provide information regarding the statement of estimated costs, or to provide a proposal for a lower regulatory cost alternative must do so in writing within 21 days of this notice.

SPECIFIC AUTHORITY: 373.044, 373.113, 373.171 FS.

LAW IMPLEMENTED: 373.036, 373.0361, 373.0395, 373.042, 373.0421 FS.

IF REQUESTED WITHIN 21 DAYS OF THE DATE OF THIS NOTICE, A HEARING WILL BE SCHEDULED AND ANNOUNCED IN THE FAW.

THE PERSON TO BE CONTACTED REGARDING THE PROPOSED RULE IS: Karen A. Lloyd, Assistant General Counsel, Office of General Counsel, 2379 Broad Street, Brooksville, FL 34604-6899, [phone], extension 4651

 

THE FULL TEXT OF THE PROPOSED RULE IS:

 

40D-8.041 Minimum Flows.

(1) Minimum Flows for the Lower Hillsborough River.

(1) through (2) renumbered (a) through (b) No change.

(2)(3) No change.

(3) Minimum Flows for Myakka River.

(a) The Minimum Flows are to ensure that the minimum hydrologic requirements of the water resources or ecology of the natural systems associated with the river are met.

(b) Minimum Flows for the Myakka River at the USGS Myakka River near Sarasota Gage USGS # 02298830 (“Sarasota Gage”) are set forth in Table 8-10 below. The long-term compliance standards set forth in Table 8-B are established based on the application of the Minimum Flows to the lowest anticipated natural flow conditions. Minimum Flows for the Myakka River are both seasonal and flow dependent. Two standards are flow-based and applied continuously regardless of season. The first is a Minimum Low Flow threshold of 0 cfs at the Sarasota Gage. The second is a Minimum High Flow threshold of 577 cfs at the Sarasota Gage. The Minimum High Flow is based on changes in the number of days of inundation of floodplain features. There are also three seasonally dependent or Block specific Minimum Flows. The Block 1 and Block 2 Minimum Flows are based on potential changes in habitat availability for fish species and macroinvertebrate diversity. The Block 3 Minimum Flow is based on changes in the number of days of connection with floodplain features.

 

Table 8-10 Minimum Flow for Myakka River at USGS Myakka River near Sarasota Gage
Period	Effective Dates	Where Flow on Previous Day Equals:	Minimum Flow Is
Annually	January 1 to December 31	0 cfs >0 cfs	0 cfs Seasonally dependent – see Blocks below
Block 1	April 20 to June 25	0 cfs >0 cfs	0 cfs previous day flow minus 15%
Block 2	October 27 to April 19	0 cfs >0 cfs	0 cfs previous day flow minus 5%
Block 3	June 26 to October 26	0 cfs >0 cfs and <577 cfs >577 cfs	0 cfs previous day flow minus 16% previous day flow minus 7%

 

(c) Compliance – The Minimum Flows are met when the flows in Table 8-11 are achieved.

 

Table 8-11 Compliance Standards for Myakka River at USGS Myakka River near Sarasota Gage
Minimum Flow	Hydrologic Statistic	Flow (cfs)
Annual Flow	10-Year Mean 10-Year Median 5-Year Mean 5-Year Median	172 12 149 5
Block 1	10-Year Mean 10-Year Median 5-Year Mean 5-Year Median	23 0 4 0
Block 2	10-Year Mean 10-Year Median 5-Year Mean 5-Year Median	28 4 15 3
Block 3	10-Year Mean 10-Year Median 5-Year Mean 5-Year Median	324 181 241 133

 

Specific Authority 373.044, 373.113, 373.171 FS. Law Implemented 373.036, 373.0361, 373.0395, 373.042, 373.0421 FS. History–Readopted 10-5-74, Amended 12-31-74, Formerly 16J-0.15, 40D-1.601, Amended 10-1-84, 8-7-00,________.

 

NAME OF PERSON ORIGINATING PROPOSED RULE: Marty Kelly, Manager, Ecologic Evaluation, Resource Conservation and Development, 2379 Broad Street, Brooksville, FL 34604-6899, [phone], extension 4235

NAME OF SUPERVISOR OR PERSON WHO APPROVED THE PROPOSED RULE: Governing Board of the Southwest Florida Water Management District

DATE PROPOSED RULE APPROVED BY AGENCY HEAD: November 30, 2005

DATE NOTICE OF PROPOSED RULE DEVELOPMENT PUBLISHED IN FAW: October 14, 2005

The District does not discriminate on the basis of disability. Anyone requiring reasonable accommodation should contact Dianne Lee at [phone], ext. 4658; TDD only: 1(800)231-6103.