80 REPORT OF INVESTIGATIONS NO. 50
water in the Orlando area. Runoff from fields that are fertilized and drainage from septic tanks contribute to pollution in the lake.
Water from Lake Hart near Narcoosee (station 21), has been analyzed semiannually since October 1954 (See table 8). This water has high color, low pH values, and low dissolved mineral content. Lake Hart is in a swampy area which contains much decaying organic material which causes the high color in the water. Decaying organic material usually contains weak organic acids which cause low pH. The mineral content of the water is low because the soil in the area is relatively insoluble. The color during the period of record ranged from 30 to 170 units. The pH ranged from 5.4 to 6.3, indicating that the water is slightly corrosive. The dissolved mineral content ranged from 20 to 52 ppm.
The water in Lake Apopka at Winter Garden (station 5) is hard and high in calcium bicarbonate, indicating inflow of water from the Floridan aquifer. During low stage in February 1963, the calcium content was 28 ppm, the bicarbonate was 156 ppm, and the water hardness was 150 ppm. The range in quality of water from Lake Apopka in table 8 shows other constituents in concentration that are higher than those in water in the Floridan aquifer near Lake Apopka. Possible sources of these constituents are waste water from nearby citrus processing plants, sewage plant and septic tank effluent, and leaching of fertilizer and pesticides applied to lands within the lake basin.
Water collected from Johns Lake at Oakland (station 25) at low stage in 1963, had a hardness of 44 ppm, a mineral content of 111 ppm, and a color of 25 units. This relatively high mineralization is probably caused by some of the fertilizer that was applied to the surrounding groves entering the lake through surface runoff and seepage of ground water.
CONTROL OF LAKE STAGES
The logical approach to control of lake levels is through control of the factors that affect them. These factors are: rainfall, evaporation, surface inflow and outflow, and underground inflow and outflow. However, rainfall and evaporation cannot be effectively controlled.
Control of lake levels through control of surface inflow has been practiced in Orange County for years. For example, water that would normally drain from Colonial Plaza into the south Orlando lakes is diverted to Lake Sue through a pipeline. Much water that would otherwise enter lakes from street drainage is