40D-8.041 Minimum Flows.

(1) through (3) No change.

(4)  Minimum Flows for upper Peace River.

(a) Over the last several decades there has been a significant decline in flow in the upper Peace River, especially during the dry season.  One of the major contributing factors is the elimination of baseflow as a result of ground water withdrawals that have lowered the potentiometric surface of the upper Floridan aquifer.  In addition, surface-water drainage alterations, reduction in surface storage, long-term cyclical declines in rainfall and karst openings in the riverbed have played significant roles in reducing flow in the upper Peace River.

(b)  The minimum flows are to ensure that the minimum hydrologic requirements of fish and natural systems associated with the river are met and not jeopardized by withdrawals.  At this time only Minimum Low Flows are being established. It is anticipated that mid- and high-minimum flows will be established once the controlling factors that affect those flows are better understood.

(c)  The Minimum Low Flows for the upper Peace River are set forth in Table 8-8 below.  The Minimum Low Flows are established based on the lowest acceptable flow under the lowest anticipated flow conditions.  This is determined by providing for the hydrologic requirements of biological communities associated with the upper Peace River system, as well as considering non-consumptive uses including fishing, wildlife observation, general recreation, aesthetic enjoyment, canoeing and boating.  This determination uses professional experience and judgment to identify key habitats and hydrologic requirements for specific biotic assemblages.  This

approach results in establishing Minimum Low Flows for the upper Peace River based on maintaining the higher of the water elevations needed for fish passage (0.6 feet or 7.2 inches) or the lowest wetted perimeter inflection point (as much stream bed coverage as possible for the least amount of flow) as set forth below.  A ninety-five percent annual exceedance occurs when the flow is greater than the Minimum Low Flow at least ninety-five percent of the days, or 350 days, of a calendar year.

(d)  Compliance – The Minimum Low Flow is achieved when the measured flow rate is at or above the Minimum Low Flow for three consecutive years.  Once the Minimum Low Flow has been achieved for three consecutive years, the Minimum Low Flow is not met when the measured flow rate is below the Minimum Low Flow for two out of ten years commencing the year after achievement.  If the two years below the minimum flow occur anytime before the ten year period is complete, the upper Peace River is deemed below its Minimum Low Flow and the three consecutive years above the Minimum Low Flow is again required for compliance.  Once the ten-year period is complete, the period will roll forward one year each year.

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,_________.

40D-8.624 Guidance and Minimum Levels for Lakes

(1) through (12) No change. 

(13) Levels for lakes established during or after August 7, 2000, are set forth in the following table. After the High Minimum Lake Level and Minimum Lake Level elevation for each lake is a designation indicating the Method used, as described in subsection 40D-8.624(7), F.A.C., to establish the level. Compliance with the High Minimum and Minimum Lake Levels is determined pursuant to paragraphs (6)(b) and (7)(b) above. Guidance Levels established prior to August 7, 2000, are set forth in Table 8-3 in subsection 40D-8.624(14), F.A.C., below.

(14) Guidance Levels established for lakes prior to August 7, 2000, are set forth in the following table:

Specific Authority 373.044, 373.113, 373.171 FS. Law Implemented 373.036, 373.0361, 373.0395, 373.042, 373.0421, 373.086 FS.  History–New 6-7-78, Amended 1-22-79, 4-27-80, 10-21-80, 12-22-80, 3-23-81, 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, 11-8-82, 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, 5-13-85, 6-26-85, 11-3-85, 3-5-86, 6-16-86, Formerly 16J-8.678, Amended 9-7-86, 2-12-87, 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, 9-30-91, 10-7-91, 7-26-92, 3-1-93, 5-11-94, 6-6-96, 2-23-97, 8-7-00, 1-8-04, 12-10-04, 6-05-05,________.

40D-8.626 Minimum Aquifer Levels in Hillsborough County North of State Road 60, and Pasco and Pinellas Counties.

(1) Hillsborough County North of State Road 60, and Pasco and Pinellas Counties Salt Water Intrusion Minimum Aquifer Levels.  Salt Water Intrusion within this area has not been regional in nature, but is of localized concern in some coastal areas.  The District has chosen the North Pinellas, Southwest Pasco and Northwest Hillsborough Counties region as the priority area for the establishment of Salt Water Intrusion Minimum Aquifer Levels (“SWIMAL”) to prevent regional seawater intrusion because of the availability of data and the potential for future intrusion.  The SWIMALs for the Upper Floridan aquifer shall be established as follows:

(1) through (3) renumbered  (a) through (c) No change.

(2) SWUCA Salt Water Intrusion Minimum Aquifer Level.

(a) The District has determined that ground water withdrawals in the SWUCA have contributed to water level declines that advance saltwater intrusion.  The coastal portion of the SWUCA in southern Hillsborough, Manatee and northern Sarasota counties (the Most Impacted Area or MIA) is a priority area for the establishment of minimum aquifer levels because of its proximity to the saltwater interface and the large effect on interface movement caused by lowering of the potentiometric surface in this area.  The Salt Water Intrusion Minimum Aquifer Level (SWIMAL) is established to stabilize regional water level declines so that long-term management efforts can slow the rate of regional saltwater intrusion in the MIA.  This is based on an average value to address the regional nature of the problem and avoids the potential for localized lowering of a minimum level.

(b)  The SWIMAL over the surface of the MIA is 13.1 feet (National Geodetic Vertical Datum of 1929 or NGVD 1929).  The SWIMAL is derived using the method set forth in (2)(c) below.

(c)  The reference period for which the SWIMAL is calculated is the period 1990 through 1999.  Ten wells from within or adjacent to the MIA (Table 8-5), are used to determine the minimum level.  The annual average elevation for each of the years 1990 through 1999 is established utilizing monthly water level data for each of the wells.  The annual averages over the period are then used to calculate the decadal average for the period.  The 1990-99 average Upper Floridan aquifer potentiometric surface of the MIA is constructed by calculating the average of these annual average values weighted spatially using the Thiessen polygon methodology.  The resulting Minimum Level over the surface of the MIA is 13.1 feet (National Geodetic Vertical Datum of 1929).

Table 8-5: Wells utilized to determine the Salt Water Intrusion Minimum Aquifer Level.

(d)   Implementation of The SWUCA Salt Water Intrusion Minimum Aquifer Level – The SWIMAL shall be used to gauge the status of the ground water resource with respect to