Weeki Wachee River System Recommended Minimum Flows and ...

6.2 Resource Criteria / Goals – Freshwater
The details of the District's protocols for setting freshwater MFL criteria and goals has
been documented elsewhere (SWFWMD 2002, Kelly et al. 2005a, 2005b, 2005c, 2007a
and 2007b) and is only briefly summarized herein 22 .
The freshwater segment of the Weeki Wachee River was evaluated using the Physical
Habitat Simulation Model (PHABSIM). Data were collected for PHABSIM analysis at
three locations (Figure 6-3) in the Weeki Wachee River watershed. Two of the sites
were in the main river and were called the "Sandbag" site and the "Wide" site. The third
site was located on the short spring run leading from Little Weeki Wachee Spring (also
known as Twin Dee's) and was named the "Little Weeki Wachee" site (Figure 6-3). For
all sites, the flow record evaluated in the PHABSIM time-series analyses was the period
1967 through 2004. Evaluation was conducted on the raw data, uncorrected for
anthropogenic impacts due to pumpage.
The Little Weeki Wachee site is located approximately 400 meters west of the main
spring. The small spring run is highly braided and surrounded by dense vegetation.
Substrate along the spring run is generally a sandy muck matrix. The Little Weeki
Wachee Spring run is estimated to flow 380 meters before emptying into the main river.
The Wide site is the most upstream PHABSIM site on the main river and is located 1.2
km downstream from the head spring. Data were collected across one transect at this
site. The site is highly representative of the upper portion of the river with moderately
high banks, a flat sand bottom, and scarce vegetation. The river is 20 meters wide at
the site under medium flow conditions.
The Sandbag site is located 1,000 meters downstream of the Wide site. The site is
representative of the middle reaches of the non-tidally influenced portions of the Weeki
Wachee River. Data were collected at three cross-sections for this site, a shoal, a run,
and a pool. The shoal for this site is composed of a mixture of natural and man-made
rocks which act as a control point for flow. The site consists of high banks on the north
shore and very low relief banks on the south. The river is an average 12 meters width
through the Sandbag site with a mixture of limerock, sand, and vegetated bottoms.
The freshwater criteria established for the Weeki Wachee was based on maintenance of
specific habitat requirements for spotted sunfish, largemouth bass, bluegill, and
macroinvertebrate diversity using habitat suitability curves within PHABSIM. A total of
twelve taxa / life stage requirements were evaluated. Initial conditions are established
for un-impacted flows and then flows are incrementally reduced (up to forty percent)
until eighty-five percent of the original habitat remains.
22 Interested readers may contact the District for copies, or may download these reports at
http://www.swfwmd.state.fl.us/documents/
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Proposed Minimum Flows and Levels for Weeki Wachee River Page 99 of 164
Resources of Concern & Criteria