Middle St. Johns - Florida Department of Environmental Protection

Water Quality Assessment Report: Middle St. Johns
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productivity are acid/clear lakes on sandy soils in Ecoregion 75. Many of
these are found on ridges and uplands.
Surface Water Resources
The Middle St. Johns Basin contains numerous surface waterbodies.
Surface waters, including lakes, streams, wetlands, and springs, occupy
almost 690 square miles, or about 34 percent of the total basin area. This
section delineates the basin’s hydrology, describes the movement and management
of water in the basin, briefly describes the major characteristics
of surface waters that influence water quality in the basin, and describes
surface water classifications and special designations.
Figure 2.3 shows the locations of the largest waterbodies. A more
detailed discussion in Chapter 3 provides information on each planning
unit.
Basin Climate and Hydraulics
Climate in the basin is characterized as warm temperate to subtropical.
The basinwide average annual temperature is 70.2º F, and annual rainfall
averages 56.51 inches based on climate records from 1971 to 2000 for
DeLand. Rainfall patterns vary spatially and temporally. About half the
annual average amount of rain falls from June through September (the wet
season). Maritime tropical masses dominate the weather during the wet
season and continental frontal systems during the rest of the year. Prevailing
winds are northeasterlies in the fall and winter and southeasterlies in
the spring and summer.
On average, 14 inches of the average 56.51 inches of rainfall each year
appear as runoff in streams and lakes (Rumenik, 1988). Runoff includes
water from rainfall that falls directly onto surface waters, flows off land, or
infiltrates into ground water and later emerges in surface waters. Surface
runoff peaks in late summer and autumn.
Streams
Streams occupy 13.3 square miles, or about 0.65 percent, of the basin.
The dominant stream feature is the St. Johns River. A variety of stream
types, ranging from blackwater to spring-fed runs, are found in the basin.
St. Johns River Main Stem
The Middle St. Johns River comprises a series of elongated lakes connected
by river segments. It is classified among Florida rivers as a large river
(Nordlie, 1990).
Water moves from south to north downstream through Lake Harney,
Lake Monroe, Lake Woodruff, and Lake George, to the confluence of
the St. Johns with the Ocklawaha River. Lakes Harney, Monroe, and
George are wide spots in the St. Johns River that, because of their width,
have the hydraulic characteristics of lakes. As the river moves downstream
from Lake Harney, its channel becomes more defined with elevated banks
(DeMort, 1991).