G. L. Giese E. F. Hubbard W.L. Yonts 1973 <p>The Geological Survey, in cooperation with the city of Durham, N. C., collected evaporation data at Lake Michie, Durham's 480-acre water-supply reservoir, for 10 consecutive years from September 1961 to September 1971. Wind speed, air temperature, and water temperature-collected continuously-were used in conjunction with water-budget data to calibrate the semi-empirical mass-transfer equation, E Nu(e_o - e_a), where E is evaporation; N is the mass-transfer coefficient, which is a constant for a given lake; u is wind speed; e_o is the vapor pressure of the saturated air at the water surface; and e_a is the vapor pressure of the surrounding air. For evaporation expressed in inches, the mass-transfer coefficient for Lake Michie is 0.0036.</p><p>During the study period the average annual evaporation from Lake Michie was 37.9 inches. Within-year variation of evaporation from the lake is sinusoidal, with a high during July averaging 4.71 inches and a low during January averaging 1.45 inches.</p><p>Evaporation from Lake Michie was 0.72 (or about three-quarters) of the evaporation from the National Weather Service evaporation pan at Chapel Hill. This ratio, called a pan coefficient, was not constant throughout the year, ranging from an average of 0.57 for April to 1.09 for December.</p> application/pdf 10.3133/wri7338 en U.S. Geological Survey Evaporation from Lake Michie, North Carolina 1961-71 reports