The amendments establish minimum flows pursuant to Section 373.042, F.S., for the upper Hillsborough River and Crystal Springs. These water bodies are listed on the District's minimum flow and levels priority list for establishment of minimum flows. ...

 

WATER MANAGEMENT DISTRICTS
Southwest Florida Water Management District

RULE NO: RULE TITLE
40D-8.041: Minimum Flows
PURPOSE AND EFFECT: The amendments establish minimum flows pursuant to Section 373.042, F.S., for the upper Hillsborough River and Crystal Springs. These water bodies are listed on the District's minimum flow and levels priority list for establishment of minimum flows. The minimum flows will be used in the District's permitting and resource management and development programs.
SUMMARY: The District has identified seasonal low, medium and high flow periods for the Upper Hillsborough River. Short-term minimum flow compliance standards were developed for each of these periods using a "building block" approach. The Minimum Low Flow for the low flow period (Block 1, April 20 through June 24) is the natural flow minus 10% at the USGS Morris Bridge gage.
For the Minimum High Flow for the high flow period (Block 3, June 25 through October 27), is a stepped flow reduction of 13% and 8% of the historic flows, with the step occurring at the 15% exceedance flow (470 cfs) at the USGS Morris Bridge gage. To protect high flows regardless of their seasonality, the high flow step of an 8% reduction for flows above 470 cfs is maintained throughout the year.
For the medium flow period (October 28 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 11% at the USGS Morris Bridge.
Five and ten year means and medians are proposed as long-term compliance standards.
A minimum flow for the Crystal Springs complex is established as 46 cfs based on a 5-year running mean and median.
SUMMARY OF STATEMENT OF ESTIMATED REGULATORY COSTS: No Statement of Estimated Regulatory Cost was prepared.
Any person who wishes to provide information regarding a statement of estimated regulatory costs, or provide a proposal for a lower cost regulatory 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, 373.042, 373.0421 FS.
IF REQUESTED WITHIN 21 DAYS OF THE DATE OF THIS NOTICE, A HEARING WILL BE SCHEDULED AND ANNOUNCED IN FAW.
THE PERSON TO BE CONTACTED REGARDING THE PROPOSED RULE IS: Karen A. Lloyd, Assistant Deputy 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) No change.

(2) Minimum Flows for the upper Hillsborough 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 upper Hillsborough River at the USGS Hillsborough River near Morris Bridge Gage USGS # 02303330 (“Morris Bridge Gage” 0) are set forth in Table 8-12 below. The long-term compliance standards set forth in Table 8-13 are established based on the application of the Minimum Flows to the lowest anticipated natural flow conditions. Minimum Flows for the upper Hillsborough 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 52 cfs at the Morris Bridge Gage. The second is a Minimum High Flow threshold of 470 cfs at the Morris Bridge 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 8-12 Minimum Flow for Upper Hillsborough River at USGS Hillsborough River near Morris Bridge Gage
Period	Effective Dates	Where Flow on Previous Day Equals:	Minimum Flow Is
Annually	January 1 to December 31	≤52 cfs >52cfs and <470 cfs 470 cfs	52 cfs Seasonally dependent  see Blocks below Previous day flow minus 8%
Block 1	April 20 to June 24	≤52 >52cfs and <470 cfs 470 cfs	52 cfs previous day flow minus 10% Previous day flow minus 8%
Block 2	October 28 to April 19	≤52 >52cfs and <470 cfs 470 cfs	52 cfs previous day flow minus 11% previous day flow minus 8%
Block 3	June 25 to October 27	≤52 cfs >52 cfs and <470cfs 470 cfs	52 cfs previous day flow minus 13% previous day flow minus 8%

 

(c) Compliance – The Minimum Flows are met when the flows in Table 8-13 are achieved.

 

Table 8-13 Compliance Standards for the Hillsborough River near Morris Bridge Gage
Minimum Flow	Hydrologic Statistic	Flow (cfs)
Annual Flow	10-Year Mean 10-Year Median 5-Year Mean 5-Year Median	190 96 149 74
Block 1	10-Year Mean 10-Year Median 5-Year Mean 5-Year Median	74 62 57 52
Block 2	10-Year Mean 10-Year Median 5-Year Mean 5-Year Median	153 89 105 72
Block 3	10-Year Mean 10-Year Median 5-Year Mean 5-Year Median	287 150 235 107

 

(2) through (5) renumbered (3) through (6) No change.

(7) Minimum Flows for Crystal Springs Located Within the Hillsborough River Basin, Hillsborough County, Florida.

(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 upper Hillsborough River are met.

(b) The Minimum Flow for Crystal Springs is stated as the flow measured by USGS physical measurements. Flows from Crystal Springs are calculated as the difference between upstream flow measurements at USGS Gage No. 02301990 – Hillsborough River Above Crystal Springs near Zephyrhills, FL and downstream flow measurements at USGS Gage No. 02302010 – Hillsborough River Below Crystal Springs near Zephyrhills, FL measurements and constitute the combined flow of the main spring vent and numerous smaller vents in the river channel. The minimum flow for the Crystal Springs complex is 46 cfs based on a 5-year running mean and median.

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, 2-6-06, 4-6-06, 1-1-07, 11-25-07,________.

NAME OF PERSON ORIGINATING PROPOSED RULE: Karen A. Lloyd, Assistant Deputy Counsel, Office of General Counsel, 2379 Broad Street, Brooksville, FL 34604-6899, [phone], extension 4651
NAME OF SUPERVISOR OR PERSON WHO APPROVED THE PROPOSED RULE: Southwest Florida Water Management District Governing Board
DATE PROPOSED RULE APPROVED BY AGENCY HEAD: December 18, 2007
DATE NOTICE OF PROPOSED RULE DEVELOPMENT PUBLISHED IN FAW: September 14, 2007; December 28, 2007