The effect of heated water on the temperature and evaporation of Hyco Lake, North Carolina, 1966-72
Water-Resources Investigations Report 11-74
By W.L. Yonts and G.L. Giese
Abstract
Three levels of thermal loading of Hyco Lake by heat from two steam-electric generators have resulted in higher temperatures and increased evaporation in the 3,750-acre (1,518 square hectometer) lake. During the winter, local temperature increases of 34 °F (19 °C) were sometimes observed at the surface as heated water spread out on top of the cooler, more-dense, lake water, affecting areas as large as 2,590 acres (1,048 square hectometers) with temperature increases averaging up to 12 °F (6.7 °C) higher than natural lake temperatures. In the summer average temperature increases at the surface seldom exceeded 6 °F (3.3 °C) and the maximum area affected was 2,570 acres (1,040 square hectometers).
Forced evaporation from the heated part of Hyco Lake increased in proportion to the added heat, reaching a maximum of 23.1 inches (586 millimeters) in 1970, as compared to 55.6 inches (1,412 millimeters) of natural evaporation for that year.
In 1969, over the heated area, 210,600 British thermal units per square foot per year or 2,407,510,000 joules per square meter per year of heat were added to the lake. Of this amount, about 58 percent of the heat was utilized for evaporation, 24 percent for back radiation, 8.0 percent was conducted as sensible heat from the lake, 1.0 percent was removed through outflow, and 0.04 percent was advected by the evaporated water. These percentages are fairly typical of the first three stages of thermal loading.
Citation:
Yonts, W.L., and Giese, G.L., 1974, The effect of heated water on the temperature and evaporation of Hyco Lake, North Carolina, 1966-72: U.S. Geological Survey Water-Resources Investigations 11-74, 38 p.
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