August 8, 1974 --
FROM THE DESK OF THE CHIEF HYDROLOGIST:
ON RELATIONSHIP OF THE WACCASASSA AND WITHLACOOCHEE BASINS
GARALD G. PARKER AND PEDRO A. HERNANDEZ
Chapter 16CB-0.03, Florida Statutes, entitled "Watershed Basins,"
states that: "Pursuant to section 5 of Chapter 61-691, Laws of Florida,
the area of the District (SWFWMD) is divided into watershed basins to
include each major stream and its tributary streams and all lands draining
therein except the Green Swamp watershed basin" (the italics are ours).
It is our intent to show that the largest part of the currently constituted
Waccasassa Basin is a tributary of the Withlacoochee; much as "the Oklawaha
is a tributary of the St. Johns, and therefore should not be transferred
out of the Southwest Florida Water Management District. The Oklawaha, on
the other hand, is a recognized part of the St. Johns River drainage.
Among the eleven basins designated by the State Legislature that
comprise Southwest Florida Water Management District are the Waccasassa
and the Withlacoochee. The latter has its headwaters in the Green Swamp
120 to 130 feet above sea level, whereas the former has much lower,
heretofore indefinite and generally poorly understood hydrologic boundaries
and drainage. In general, boundaries of the designated river basins follow
surface-water divides, excepting the Green Swamp Basin. However, the
boundary lines are stair-stepped along Section, Township and Range boundaries
to simulate the topographic divides (Figure 1). This was done for con-
venience in the assessment of taxes inasmuch as property boundaries normally
follow the land-survey grid, not topographic or hydrologic features such
as stream or surface-drainage divides.
Those who were charged with drawing the boundaries had difficulty in
some areas discerning drainage divides because of the non-existence of
discernable stream headwaters even in those areas having good or reasonably
good topographic maps. Some parts of the District are not covered yet by
topographic mapping and for the remaining mapped area, the maps usually
have only 10-foot contour intervals. Thus, in very flat and swampy areas
it is almost impossible to determine just where a stream begins or, in
downstream swampy areas, even where its channel should be located. It
follows that some unavoidable errors were made in drawing basin boundaries.
In addition to these errors are those caused by the fact that surface-
water basins, as discriminated by topographic divides, do not always coincide
with natural ground-water divides. In fact, in this District, as shown
on Figure 1 and 2, they more often do not.
August 8, 1974
Thus it was that, when the Waccasassa Basin was drawn, it included a
total area of about 1,220 square miles. But more than 72 percent of this
vast area, lying in its eastern part, is drained not by the Waccasassa
River, which has a drainage of only about 550 square miles, but by ground-
water discharge into Rainbow Spring and by numerous smaller springs and
seeps into Rainbow (Blue) Run. The area involved in this large ground-
water drainage is about 876 square miles and its total runoff is to the
Withlacoochee at a line-juncture east of Dunnellon. Figure 1 shows, by
means of arrows indicative of regional ground-water flow, the area con-
tributing drainage to the Withlacoochee. Other arrows indicate flow to
other places of discharge, and by drawing lines between divergent flow
patterns, ground-water basins are defined.
Figure 2 shows the northern part of Figure 1, enlarged and without
ground-water flow arrows. Unfortunately, this information had not been
prepared prior to the time that the original basin boundaries were established,
Chapter 61-691, Florida Statutes, 1961, nor was such information available
at the time the subsequent decision was made to transfer the Waccasassa
Basin to the new Suwannee River Basin Water Management District, Chapter
72-299, Florida Statutes, 1972. With the new information now available
(Figures 1 and 2), it can be shown that the 876 square miles of the
Waccasassa Basin's Rainbow Springs-Blue Run drainage constitutes the
major tributary to the Withlacoochee River.
Both the map makers of 1961 and the recent map changers of 1972
recognized that Rainbow Spring and Blue Run, of themselves, constitute a
tributary system to the Withlacoochee, consequently the basin boundary
is drawn so as to include Rainbow Spring and Blue Run within the Withlacoochee
Basin. However, lacking an understanding of the extent of the lands
draining thereto, the boundary delineators excluded this tributary area
to Rainbow Spring and Blue Run from the Withlacoochee Basin.. This excluded
area produces more runoff per square mile (14.49 inches per year) than any
other part of the Withlacoochee River Basin.
The Withlacoochee River's main stem, from its origin in the wetlands
of the Green Swamp east of Eva to its mouth in Withlacoochee Bay west of
Yankeetown, is some 140 miles long. Not counting the Rainbow Springs
drainage area, the Withlacoochee's drainage area is about 2,020 square
miles. Including it would increase the river basin's size to about 2,896
Flow of the Withlacoochee must be estimated in its lower 38 miles.
The river is tidal below the Inglis Dam, eleven miles inland from the river's
mouth. Lake Rousseau occupies that part of the river valley upstream from
Inglis Dam for a distance of about 13 miles. The first U. S. Geological Survey
stream-gaging station upstream from the mouth that is unaffected by tides,
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August 8, 1974
lake backwater, or lockage and releases of flow to the bypass, channel is near
Holder, 38 miles above the mouth. Holder is the farthest-downstream gaging
station on the Withlacoochee River before flow enters Lake Rousseau. Its
average discharge is about 752 mgd or 8.65 inches per year, but unmeasured
flow of about 10 mgd, between Holder and Lake Rousseau increases the total
average river inflow to the lake to about 762 mgd or 8.78 inches per year.
Additional inflow to Lake Rousseau of about 509 mgd or about 14.5 inches'
per year comes from Rainbow Spring and the 5-mile-long Blue Run. Thus
total average daily stream inflow to the lake is 762 mgd + 509 mgd = 1,271 mgd.
At average flow rates, Rainbow Spring drainage contributes 509 of the
total inflow, or 40 percent of the total inflow into'Lake Rousseau. Truly,
this makes the Rainbow Spring tributary drainage basin the principal tributary
to the Withlacoochee River even in times of average flow.
But its importance can be determined better by comparing the 95 percent
duration flows of-these two tributaries to the lower Withlacoochee River. The
95 percent flow duration is that flow which equals or exceeds the values
indicated on a flow-duration curve of a given stream 95 percent of the time;
it is a time of low flow, such as occurs during long periods of dry weather
when water-supply is in greatest demand.
At such periods of low flow, the quantity entering Lake Rousseau from
the upper Withlacoochee is about 165 mgd whereas the flow from the Rainbow
tributary area contributes 390 or about 70 percent of the total flow into
the Lower Withlacoochee; by contrast, the Upper Withlacoochee only contributes
30 percent. Thus, the Rainbow Spring drainage basin is a prime tributary to
the Withlacoochee, much as the Oklawaha River basin is a tributary to the
St. Johns River basin.
It has been shown above that the Rainbow Spring hydrologic system, con-
sisting of 5-mile-long Rainbow (Blue) Run, the springs themselves, and the
contributary extensive underground drainage system comprise, in total, a
prime tributary system to the Withlacoochee and thus comprise an integral part
of the Withlacoochee Basin. This the Waccasassa River Basin Board recognized
in its Resolution No. 12, dated January 17, 1974, requesting that the
Waccasassa Basin not be transferred to the Suwannee River Water Management
District but be retained in the Southwest Florida Water Management District.
Subsequently the District Board of Governors, on April 10, 1974, by their
Resolution No. 540 requested that statutory amendments be made to the Florida
Water Resources Act of 1972'permitting the Waccasassa Basin to remain a part
of the Southwest Florida Water Management District. This request includes
not only the Rainbow drainage system of 786 square miles within the Waccasassa
Basin but the true Waccasassa River drainage area of about 547 square miles.
The latter is an independent river basin lying between the Withlacoochee River
August 8, 1974
basin on the south and the-Suwannee River basin on the north. Although the
Waccasassa River basin not a part of either of these huge river systems it is
more closely allied with the Withlacoochee than with the Suwannee. It should
be retained in the Southwest Florida Water Management District and not be
transferred to the hydrologically unrelated Suwannee Water Management District
which lies entirely north of the Peninsular Florida Hydrologic Divide which
separates the Suwannee from the Waccasassa, Withlacoochee and Silver Springs
August 8, 1974
TO: DONALD R. FEASTER, EXECUTIVE DIRECTOR
FROM: GARALD G. PARKER,,SENIOR SCIENTIST AND CHIEF HYDROLOGIST
SUBJECT: ESSAY "ON RELATIONSHIP OF THE WACCASASSA
AND WITHLACOOCHEE BASIN"
Attached is a copy of the above essay prepared by myself and Pedro Hernandez.
It is a condensed version of a.longer report of which Pedro will be the senior
author and which he hopes to prepare for delivery before the American Water
Resources Association meeting in Puerto Rico in November, 1974.
This essay is designed for publication in the Hydroscope.
cc: Chairman, Board of Governors
Members, Board of Governors
Members, Waccasassa Basin Board
Rodney N. Cherry
James A. Mann
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