40D-8.041: Minimum Flows
PURPOSE AND EFFECT: To amend Rule 40D-8.041, F.A.C.m to establish Minimum Flows for the Lower Alafia River System as required pursuant to Section 373.042, Florida Statutes. For purposes of this rule the Lower Alafia River System includes the watercourse downstream of the USGS Gage No. 02301500 Alafia River at Lithia, FL including Lithia Springs, Buckhorn Spring, and their associated spring runs.
SUMMARY: The Minimum Flow is proposed as 81% of the daily flow to the Lower Alafia River System that is above 120 cfs. Flow to the lower river is calculated as flow at the United States Geological Survey gaging station Alafia River at Lithia (multiplied by a factor of 1.117 to account for flow between the gage and Bell Shoals Road), plus flows from Lithia and Buckhorn Springs. In addition, a Low Flow Threshold (LFT) of 120 cubic feet per second (cfs) is proposed which prohibits all withdrawals from the river and springs when flows in the lower river fall are below that rate of flow. Minimum five-year and ten-year moving average values are set forth in the rule as a tool to assess whether flows to the Lower Alafia River remain above flow rates that are expected to occur with implementation of the Minimum Flow.
SUMMARY OF STATEMENT OF ESTIMATED REGULATORY COSTS: Only two permittees currently withdraw water from the Alafia River. Only one is expected to be affected by the proposed minimum flow. No significant costs are anticipated to the agency or other state or local governments. There are no small businesses with water use permits withdrawing from the Lower Alafia River and therefore there are no impacts to existing small business permittees from the proposed establishment of the minimum flow. It is unknown whether in the future any small business will seek a water use permit for withdrawals from the Lower Alafia River System that would impact the proposed Minimum Flow. If withdrawals from surface water during the low flow periods impact the proposed minimum flow, individuals and entities have various mitigation options:
a) Groundwater may be used to augment the flow of the Lower Alafia if the applicant is able to provide a net benefit. The net benefit will be in the form of a retirement of historically used quantities. These quantities should equal the amount of the predicted impact plus 10%.
i. Cost: 0.24 per 1,000 gallons
b) The applicant may suspend or avoid surface water withdrawals during the low flow season and purchase reclaimed water.
i. Incremental Cost: $2.56 per 1,000 gallons
c) The applicant may suspend or avoid surface water withdrawals during the low flow season and use storm water.
Incremental Cost: $1.07 per 1,000 gallons
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, 2379 Broad Street, Brooksville, FL 34605
THE FULL TEXT OF THE PROPOSED RULE IS:
40D-8.041 Minimum Flows.
(1) through (9) No change.
(10) Minimum Flows for Alafia River Freshwater Segment.
(a) through (c) No change.
(11) Minimum Flow for Lower Alafia River System.
(a) For purposes of this rule, the Lower Alafia River System includes the watercourse downstream of the USGS Gage No. 02301500 Alafia River at Lithia, FL (the Alafia River at Lithia Gage) including Lithia Springs, Buckhorn Spring, and their associated spring runs.
(b) The Minimum Flow is to ensure that the minimum hydrologic requirements of the water resources or ecology of the natural systems associated with the Lower Alafia River System are met. Daily flows to the Lower Alafia River System are calculated by multiplying mean daily flow values at the Alafia River at Lithia Gage by a factor of 1.117, then adding the mean daily flows from Lithia Spring Major and Buckhorn Spring. Flows are calculated in the absence of withdrawals and are based on mean flows at the Alafia River at Lithia Gage from the previous day and the most recently recorded periodic values from Lithia Spring Major and Buckhorn Spring. The Minimum Flow for the Lower Alafia River System is intended to preserve 81% of the natural flow to the Lower Alafia River System when flows exceed a low-flow threshold of 120 cfs.
(c) The Minimum Flow is 81% of the daily flow to the Lower Alafia River System that is above 120 cfs.
(d) Minimum five-year and ten-year moving average values are set forth in Table 8-19 as a tool to assess whether flows to the Lower Alafia River remain above flow rates that are expected to occur with implementation of the Minimum Flow. These values represent minimum values of the averages of yearly mean and median flows to the Lower Alafia River System calculated over moving five-year and ten-year periods. These values were calculated by applying the potential maximum withdrawals that do not violate the Minimum Flow to historic flow records. It is, therefore, expected that flows to the Lower Alafia River System will not go below these values if compliance with the Minimum Flow is maintained. However, future climatic conditions or structural alterations in the watershed of the Lower Alafia River System could potentially affect surface water or ground contributions to the Lower Alafia River Systems flow regime. The District will, therefore, periodically evaluate whether these minimum moving average values expected with application of the Minimum Flow, or other factors, have possibly caused flows in the Lower Alafia River System to decline.
|
Table 8-19 Minimum Values of Five-year and Ten-year Moving Averages of Yearly Mean and Median Flows to the Lower Alafia River System | |
|
Value |
Flow (cfs) |
|
Minimum 10-Year Moving Average (Based On Yearly Mean Flows) |
247 |
|
Minimum 10-Year Moving Average Median (Based On Yearly Median Flows) |
150 |
|
Minimum 5-Yearly Mean Flows (Based on Yearly Mean Flows) |
217 |
|
Minimum 5 Year Moving Average (Based On Yearly Median Flows) |
120 |
Flows to the Lower Alafia River System were estimated for the period of record at the Alafia River at Lithia Gage. The period from 1987 to 2003 was used to create a relationship between daily flows at the Gage and total flows to the Lower Alafia River System. Five-year and ten-year moving average statistics were then calculated for estimated long-term flows to the Lower Alafia River System that were derived from the Alafia River at Lithia Gage.
(12)(11) No change.
Rulemaking Specific Authority 373.044, 373.113, 373.171 FS. Law Implemented 373.036, 373.0361, 373.042, 373.042 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, 2-18-08, 3-2-08, 5-12-08, 5-10-09,________.
