Minimum Flows

 

WATER MANAGEMENT DISTRICTS

Southwest Florida Water Management District

RULE NO.:RULE TITLE:

40D-8.041Minimum Flows

NOTICE OF CHANGE

Notice is hereby given that the following changes have been made to the proposed rule in accordance with subparagraph 120.54(3)(d)1., F.S., published in Vol. 46 No. 10, January 15, 2020 issue of the Florida Administrative Register.

 

THE FULL TEXT OF THE PROPOSED RULE CHANGE IS:

 

40D-8.041 Minimum Flows. 

(1) through (15) No change.

(16) Minimum Flow for the Chassahowitzka River System.

(a) For purposes of this rule, the Chassahowitzka River System includes the watercourse from the Chassahowitzka Main Springs Complex to the Gulf of Mexico, including contributing tributaries and all named and unnamed springs that discharge to the Chassahowitzka River, and Blind Springs.

(b) The Minimum Flow for the Chassahowitzka River System is 92% of the natural flow as measured at the United States Geological Survey (USGS) Gage Chassahowitzka River near Homosassa Gage No. 02310650. Natural flow is defined for the purpose of this rule as the flow that would exist in the absence of water withdrawal impacts. The Minimum Flow is based on an 8% reduction from the natural flow of 61 cubic feet per second, which was adjusted for groundwater withdrawals using hydrologic modeling for the period of record from February 20, 1997, through October 15, 2018, at the USGS Chassahowitzka River near Homosassa, FL Gage No. 02310650.

(c) Status assessments of the Minimum Flow for the Chassahowitzka River System will be completed to determine whether the flow is below or projected to fall below the Minimum Flow. Each status assessment is independent from and not a determination of water use permit compliance or environmental resource permit compliance. Permit compliance is a regulatory function that is not within the scope of this subsection. As part of each status assessment, the District will use the following approach:

1. The District will evaluate the Minimum Flow annually to determine the extent to which the flow of the Chassahowitzka River System has been reduced due to withdrawals as of the date of each status assessment at the USGS Chassahowitzka River near Homosassa, FL Gage No. 02310650. The annual evaluation will be completed through a review of:

(a) flow data;

(b) water withdrawals;

(c) aquifer water levels;

(d) rainfall data; and

(e) hydrologic modeling.

2. The District will also evaluate the Minimum Flow every five years as part of the regional water supply planning process. This evaluation will include the use of hydrologic modeling.

3. If the Minimum Flow is being met based on the annual evaluation or the evaluation performed as a part of the regional water supply planning process, then no further actions are required beyond continued monitoring.

4. If the annual evaluation indicates the flow is below the Minimum Flow, or if the flow is projected to fall below the Minimum Flow within 20 years based on the evaluation performed as a part of the regional water supply planning process, the District will conduct a causation analysis to evaluate the potential causes of impacts on the Chassahowitzka River System. 

5. Based on the causation analysis, the District will re-evaluate the Minimum Flow for the Chassahowitzka River System, or adopt a recovery or prevention strategy consistent with the provisions of Section 373.0421(2), F.S.

(d) The District will reevaluate the Minimum Flow by December 2029.

(17) Minimum Flow for the Homosassa River System.

(a) For purposes of this rule, the Homosassa River System includes the watercourse from the Homosassa Main Springs Complex to the Gulf of Mexico, including the southeast fork of the Homosassa River, Halls River, Hidden River and all named and unnamed springs that discharge to the Homosassa River.

(b) The Minimum Flow for the Homosassa River System is 95% of the combined natural flow as measured at the United States Geological Survey (USGS) Homosassa Springs at Homosassa Springs, FL Gage No. 02310678, and the USGS SE Fork Homosassa Spring at Homosassa Springs, FL Gage No. 02310688. Natural flow is defined for the purpose of this rule as the flow that would exist in the absence of water withdrawal impacts. The Minimum Flow is based on a 5% reduction from the combined natural flow of 149 cubic feet per second, which was adjusted for groundwater withdrawals using hydrologic modeling for the period of record from October 1, 2000, through October 1, 2018, at the USGS Homosassa Springs at Homosassa Springs, FL Gage No. 02310678 and the USGS SE Fork Homosassa Spring at Homosassa Springs, FL Gage No. 02310688.

(c) Status assessments of the Minimum Flow for the Homosassa River System will be completed to determine whether the flow is below or projected to fall below the Minimum Flow. Each status assessment is independent from and not a determination of water use permit compliance or environmental resource permit compliance. Permit compliance is a regulatory function that is not within the scope of this subsection. As part of each status assessment, the District will use the following approach:

1. The District will evaluate the Minimum Flow annually to determine the extent to which the flow of the Homosassa River System has been reduced due to withdrawals as of the date of each status assessment at the USGS Homosassa Springs at Homosassa Springs, FL Gage No. 02310678 and the USGS SE Fork Homosassa Spring at Homosassa Springs, FL Gage No. 02310688. The annual evaluation will be completed through a review of:

(a) flow data;

(b) water withdrawals;

(c) aquifer water levels;

(d) rainfall data; and

(e) hydrologic modeling.

2. The District will also evaluate the Minimum Flow every five years as part of the regional water supply planning process. This evaluation will include the use of hydrologic modeling.

3. If the Minimum Flow is being met based on the annual evaluation or the evaluation performed as a part of the regional water supply planning process, then no further actions are required beyond continued monitoring.

4. If the annual evaluation indicates the flow is below the Minimum Flow, or if the flow is projected to fall below the Minimum Flow within 20 years based on the evaluation performed as a part of the regional water supply planning process, the District will conduct a causation analysis to evaluate the potential causes of impacts on the Homosassa River System. 

5. Based on the causation analysis, the District will re-evaluate the Minimum Flow for the Homosassa River System, or adopt a recovery or prevention strategy consistent with the provisions of Section 373.0421(2), F.S.

(d) The District will reevaluate the Minimum Flow by December 2029.

(18) through (21) No change.

Rulemaking Authority 373.044, 373.113, 373.171 FS. Law Implemented 373.036, 373.042, 373.0421 FS. History–New 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, 2-18-08, 3-2-08, 5-12-08, 5-10-09, 3-23-10, 3-28-10, 7-12-10, 8-2-10 (8), 8-2-10 (15), 10-16-12, 3-20-13(16), 3-20-13(17), 6-20-16, 3-15-18, 6-19-18, __.