Lake Istokpoga
The data summarized below are data collected by Lakewatch volunteers. Additional data has been collected by the South Florida Water Management District and through our office. A summary of this additional data and some of the work being done on Lake Istokpoga can be found on our current projects/Istokpoga water quality page. Water quality is discussed separately for the north and south ends of the lake since the lake is so large and there is a difference in water quality between the inlet end (north lake) and the outlet end (south lake).
Lake Istokpoga is a 28,000 acre lake located to the east of US 27 and south of the City of Sebring and north of the Town of Lake Placid. 'Istokpoga' is a Native American word meaning 'waters of death.' The lake is the 5th largest lake in Florida, it flows into the Kissimmee River and Lake Okeechobee through its outlet, the C-41a canal, and is unlike any other lake in Highlands county, being located in the Kissimmee/Okeechobee Lowland Lake Region of Florida. Most of the other lakes in Highlands County flow into Lake Istokpoga, either through surface flow or groundwater flow. The lake is very shallow, with a maximum depth of 8 feet and an average depth of only 3.5 feet. The lake is home to several thousand alligators, a good largemouth bass population and countless birds and other wildlife. For more information, please visit the Friends of Istokpoga website. Hydrilla and tussock formation are serious issues faced by this lake and are discussed on our current projects page. Overall, there appeared to be at least a temporary decline in water quality since early 2001.
North Istokpoga Water Quality - Lakewatch data
Water quality at the north end of Lake Istokpoga is not as good as water quality at the south end of the lake. Nutrient levels are higher compared to the south end of the lake due to the nutrients entering through Arbuckle and Josephine Creeks. Phosphorus levels range from 29 to 345 ppb (parts per billion) and average 73 ppb. Nitrogen levels are also somewhat high, ranging from 600 to 2250 ppb and averaging 1270 ppb. Algae levels, as estimated by the concentration of chlorophyll in the water, increase and decrease as nutrient levels increase and decrease. Chlorophyll levels range from a very low 2 ppb to a high 120 ppb, averaging 42 ppb. The presence of algae reduces water clarity, which is measured as the depth to which a standardized 'secchi' disc can be seen when lowered into the water. Secchi depths in north Istokpoga range from 1 to 4 feet and average 2.1 feet. Water quality in the north lake itself does not appear to have changed since Lakewatch sampling began in 1996, though concentrations of nutrients in the water entering the lake have increased. Click here to view North Istokpoga water quality data by year.
South Istokpoga Water Quality - Lakewatch data
Water flows from the north end of the lake towards the S-68 outlet structure at the southeast end of the lake, and the aquatic plants growing in the lake appear to remove phosphorus from the water along the way, making south Istokpoga water significantly 'cleaner,' with respect to phosphorus but not nitrogen, than north Istokpoga water. Phosphorus levels at the south end of the lake range from 13 to 115 ppb and average 53 ppb. Nitrogen levels range from 640 to 2810 ppb and average 1265 ppb. The lower phosphorus levels in this water result in slightly lower algae populations. Chlorophyll concentrations range from 1 to 117 ppb and average 37 ppb. The water is slightly clearer as a result of slightly fewer algae present - secchi depths range from 1.3 to 9.5 feet and average 3 feet. Water quality fluctuates, as expected, but changes seem to last longer in the south end of the lake compared to the north end. Nitrogen levels also appear to be slightly higher now than they were when sampling began in 1996. More information about nutrient dynamics in Istokpoga is provided on our current projects/Istokpoga water quality page. Click here to view South Istokpoga water quality data by year. As you can see, water quality is better in the south end of the lake compared to the north end, but water quality has also declined more in South Istokpoga, compared to the north, in recent years.
There are numerous boat ramps on Lake Istokpoga. There is a ramp at the north end of the lake, just off of US 98, at Istokpoga Park near Lorida, east of Arbuckle Creek. There is another boat ramp on the southwest corner of the lake at Windy Point. Take Highlands Avenue north from County Road 621 and turn right on boat ramp road. There are two more boat ramps on the west side of the lake, one on Rutledge Avenue off of Highlands Avenue and the other at Henderson's Fish Camp - there is a fee to use these ramps. You can access the lake by launching from the RV Park on Arbuckle Creek at State Road 98 - there is a small fee to launch here as well. A final boat ramp is located on the east side of the lake off of Cowhouse Road.
Historic aerial photo gallery 1944-2002
Lakewatch water quality data through 1999 - South Lake
Lakewatch water quality data through 1999 - North Lake