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Discharges changed on Harris Chain of Lakes
Updated on 1/6/2012
12-13-2011
During the past five years, rainfall in the Upper Ocklawaha River basin has been substantially below normal. In 2010, the amount of rainfall received in this area was 2.97 inches below normal and in 2011 is 3.55 inches below normal (year-to-date through Dec. 7). These dry conditions have led to declining water levels in all of the lakes within the Harris Chain, with current lake levels all below minimum desirable levels.
To help reduce lake level declines during the winter months, when continued dry conditions are forecast, the St. Johns River Water Management District is temporarily reducing discharges from the three water control structures in the system. The amount of water being held back is minimal, particularly since discharges were already low due to below normal lake levels.
Under this temporary reduction, discharges at the Apopka-Beauclair Lock and Dam will be eliminated and discharges of water through the Burrell Lock and Dam on Haynes Creek will be reduced to 5 cubic feet per second (cfs). The minimum flows at the Moss Bluff Lock and Dam will be reduced to no more than 7 cubic feet per second.
In winter 2010, the District initiated a five-month pilot study to measure the effect of reducing discharges from these structures during the dry season. The reduced discharges helped increase water levels by about 6 inches in all of the lakes.
After receiving input from residents and businesses along Lake Griffin, the District modified the reduction schedule to allow more water to move through the structures into Lake Griffin. The discharge at the Burrell structure is 5 cfs more than last year and the discharge at the Moss Bluff structure has been reduced from 10 to 7 cfs. This change will add 8 more cfs in Lake Griffin than what was maintained during last year’s reduction, thus keeping the lake levels more equitable.
The District will closely monitor conditions and levels on all of the lakes and adapt the minimum discharge strategy to try to keep the level of each lake at or above its minimum desirable level and achieve the best possible outcome for the health of the lakes during the dry season. The temporary changes began on Dec. 8, 2011, and will end no later than April 30, 2012, and could end sooner depending on the weather.
12-13-2011
Additional information
The District is in the process of collecting and analyzing data as part of its work to revise lake level regulations and set minimum flows and levels (MFLs) for Lake Apopka and the entire Harris Chain of Lakes. MFLs are the minimum water levels and flows necessary to prevent significant harm to the water resources or ecology of an area, and MFLs define how often and for how long high, average and low water levels and/or flows should occur to prevent significant harm. Adopting MFLs for lakes Apopka, Beauclair, Dora, Harris, Eustis and Griffin remains on schedule for completion in 2014. It is anticipated that the MFL process will result in establishing minimum discharges for the three water control structures, consistent with maintaining the lakes’ minimum levels.
Updated on 1-6-2012
