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Chapter 1 Minimum Flows and Levels - Southwest Florida Water ...

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<strong>Chapter</strong> 2 BASIN DESCRIPTION WITH EMPHASIS ON<br />

LAND USE, HYDROLOGY AND WATER QUALITY<br />

2.1 Overview<br />

This chapter includes a brief description of the Braden River watershed <strong>and</strong> is<br />

followed by a presentation <strong>and</strong> discussion of l<strong>and</strong> use, hydrology, <strong>and</strong> water<br />

quality data relevant to the development of MFLs on the upper, freshwater<br />

segment of the Braden River above the USGS Braden River at Linger Lodge<br />

near Bradenton FL gage site (or alternatively above the Bill Evers Reservoir).<br />

L<strong>and</strong> use changes within the basin are evaluated to support the hydrology<br />

discussion that follows <strong>and</strong> to address the potential impact of l<strong>and</strong> use changes<br />

on river flow volumes. Flow trends <strong>and</strong> their potential causes are discussed for<br />

the Braden River <strong>and</strong> compared with other regional rivers to provide a basis for<br />

identifying benchmark periods <strong>and</strong> seasonal flow blocks that are used for a<br />

building block approach in the establishment of minimum flows. <strong>Water</strong> chemistry<br />

changes are discussed to illustrate how l<strong>and</strong> use changes may have affected<br />

observed trends in certain water quality parameters, <strong>and</strong> to demonstrate how<br />

these trends are useful in interpreting flow changes over time.<br />

2.2 <strong>Water</strong>shed Description (material in this section was taken largely from<br />

DelCharco <strong>and</strong> Lewelling, 1997).<br />

2.2.1 Geographic Location<br />

The Braden River is the largest tributary to the Manatee River, which empties<br />

into the southern portion of Tampa Bay (Figure 2-1). In 1936, the Braden River<br />

was dammed approximately six miles upstream from its mouth with a weir<br />

structure, named the John Ward Dam, to provide a freshwater source for the City<br />

of Bradenton. The initial dam was a 838-foot broad-crested weir which created a<br />

backwater effect extending approximately 6 miles upstream. The resulting 167-<br />

acre reservoir was named Ward Lake <strong>and</strong> stored approximately 585 million<br />

gallons. The reservoir was exp<strong>and</strong>ed in 1985 to 359 acres <strong>and</strong> storage capacity<br />

was increased to 1,400 million gallons by dredging the channel <strong>and</strong> surrounding<br />

riverbank upstream of the weir. Ward Lake was renamed the Bill Evers<br />

Reservoir at that time. Approximately 90 percent of the 83 square mile<br />

watershed lies within Manatee County, <strong>and</strong> the remaining 10 percent lies in<br />

northern Sarasota County. DelCharco <strong>and</strong> Lewelling (1997) identified three<br />

segments to the Braden River; the lower, middle <strong>and</strong> upper. The lower segment<br />

is the area downstream of the Evers Reservoir <strong>and</strong> is the estuarine portion of the<br />

river. The middle segment is essentially the reservoir, <strong>and</strong> the upper segment<br />

was identified as an incised channel free of any backwater effect. For the<br />

establishment of MFLs outlined in this report, the upper Braden River is defined<br />

2-1

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