publications > circular > Circular 1134 > water and environmental stress > degradation of water quality > lake okeechobee U.S. Department of the Interior U.S. Geological Survey Circular 1134 Water and Environmental Stress Degradation of Water Quality Lake Okeechobee Water quality in Lake Okeechobee has been degraded by large-scale inflow from streams that drain agricultural land on the northern side of the lake and by backpumping from canals in the EAA to the south (Klein and others, 1975). Agricultural wastes are washed from farmlands into canals during heavy runoff. During high-water periods, excess water is sometimes backpumped from the EAA into Lake Okeechobee to prevent crop damage. The average concentration of dissolved solids of the inflow from the north and from the EAA is higher than anywhere else in south Florida, excluding the saltwater areas, and at times, it is more than three times the average in the Big Cypress Swamp. The high concentration of dissolved solids is partly the result of irrigating with highly mineralized water (Klein and others, 1975). Water-quality and biologic data collected in 1969 and 1970 indicate that Lake Okeechobee was in an early eutrophic condition by the late 1960's (Joyner, 1971; 1974). The rate of eutrophication is of major concern because the lake is the primary surface reservoir in southeast Florida. Overenrichment could seriously impair its water quality and, thereby, affect downstream water users. Joyner (1971) reported that the growth of algae increased greatly between January and July 1970. The dominant species also changed from a green alga, which is indicative of early eutrophic conditions, to a blue-green alga, which is indicative of late eutrophic conditions. Inflow to the lake increased at this time because of channel improvement and accelerated inflow from its major tributary, the Kissimmee River. After channelization of the Kissimmee River, water flow through the flood plain marshes was reduced. During the last 15 years, phosphorus concentrations have increased 21/2 times in Lake Okeechobee; peak levels were reached in 1987-88. Recent occurrences of massive, lakewide blooms of blue-green algae are viewed as another sign that the lake is receiving excessive amounts of nutrients, primarily phosphorus, which threaten the overall health of the lake resources. Preliminary evidence indicates that the lake's sediments may be losing their ability to assimilate additional phosphorus loadings. Lakewide nitrogen-to-phosphorus ratios also have declined over the same period and may have favored the shift from the normal algal flora of the lake to less desirable blue-green species. These data suggest the lake may be in a phase of transition from its present eutrophic condition to a higher trophic (hypertrophic) state. Loss of the lake as a recreational fishery or potable water supply would be a major economic loss to the region. Phosphorus has been considered to be the key element that controls the growth of these nuisance algae. Therefore, to prevent further eutrophication of the lake, the primary water management strategy has been to limit and control phosphorus inflows (South Florida Water Management District, 1992). Recent research, however, has shown that primary productivity is most often limited by nitrogen or light (N.G. Aumen, South Florida Water Management District, written commun., 1994). Next: Degradation of water quality in the Big Cypress Swamp Go to top Return to Publications Page

U.S. Department of the Interior, U.S. Geological Survey
This page is: http://sflwww.er.usgs.gov/publications/circular/1134/wes/lo.html
Comments and suggestions? Contact: Heather Henkel - Webmaster
Last updated: 02 November, 2004 @ 07:32 AM(KP)