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> report 83-4126
U.S. Department
of the Interior
U.S. Geological Survey
WRI 83-4126
Chemical and Hydrologic Assessment
Of The Caloosahatchee River Basin,
Lake Okeechobee To Franklin Lock, Florida
Water-Resources Investigations Report 83-4126
Henry R, La Rose and Benjamin F.
McPherson
ABSTRACT
Annual discharge
( 1970-79 ) from Lake Okeechobee to the Caloosahatchee River averaged 51
percent of the total river discharge at Franklin Lock and ranged from 10
to 71 percent of total discharge. Excluding rainfall on the river surface
and upstream seepage, surface and subsurface runoff from the basin accounted
for the remaining total river discharge at Franklin lock.
Concentrations of
dissolved oxygen in the river (1976-79 ) ranged from less than 1 to 13 milligrams
per liter. Concentrations fluctuated seasonally; they are lower in late
summer and early autumn than during other seasons. Concentrations were lower
at the headwaters site at Moore Haven than at downstream sites.
Specific conductance
and ionic composition in the headwaters of the river have changed over the
last 35 years. In the early 1940's, specific conductance ranged from about
200 to 500 micromho per centimeter, compared with an average of about 660
micromho per centimeter in 1975-79. Also over this span, sodium, chloride,
magnesium, and sulfate increased in relative abundance compared with calcium
and bicarbonate.
Nitrogen and phosphorus
were in sufficient supply most of the time to support algal growth in the
river. Nitrite plus nitrate nitrogen was the predominant form of inorganic
nitrogen. During algal blooms, however, nitrite plus nitrate nitrogen was
depleted and probably became the limiting constituents to algal growth.
Average concentrations of nitrite plus nitrate were lower in most tributaries
than in the river. Average concentrations of total phosphorus in many of
the tributaries fell within the same range as that in the river (0.08 to
0.15milligrams per liter), but some tributaries had lower average concentrations,
and others in the eastern subbasins had higher average concentrations than
the river.
Contributions of
nitrite plus nitrate, orthophosphate, and total phosphorus from the basin
and the river substantially exceeded the contributions from Lake Okeechobee,
while contributions of ammonia nitrogen from the basin and river were quite
small compared with those from the lake. Oxidation of organic material and
ammonia in the river probably accounts for some of the downstream increase
of nitrite plus nitrate and for the relatively small increase of ammonia
nitrogen.
(The entire report is available below.)
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