National Geographic : 1948 Apr
Fleecy Clouds Float Lazily over Newly Built Kentucky Dam To cross the Tennessee River, tracks of the Illinois Central Railroad are laid on top of the dam. At left are navigation locks. Below the dam, cultivated fields and patches of woods appear; above spreads the lake, 185 miles long, inundating former farms and pastures to create inlets and islands. With 2,380 miles of shore line, this is the largest body of water impounded behind any of the TVA dams. Most observant was a Chinese engineer I talked with. He wanted to see how we have slowed down a racing river and made it "walk" through a basin nearly as large as England. Here, with forty or fifty of his countrymen, he was learning what American methods and machines may do to help China battle the floods which for centuries have ravaged the unhappy valleys of the dangerous Yellow and Yangtze Rivers.* Mosquito Control Methods Studied Government officials, engineers, doctors, scientists, writers, and agronomists flock here from India, Russia, Poland, Britain, and France. From Latin America, with all its problems of irrigation and undeveloped water power, have come more than 200 experts. *See "Taming 'Flood Dragons' Along China's Hwang Ho (Yellow River)," by Oliver J. Todd, NATIONAL GEOGRAPHIC MAGAZINE, February, 1942. Australia sent a medical officer to see how TVA fights malaria. It kills mosquitoes by spraying marshy spots, lake edges, etc., with DDT and, lately, experimentally with 2,4-D, to kill aquatic vegetation which favors mos quito development. Some oil is used, but that method is largely outmoded. Another method used is that of fluctuating the level of water behind the dams, during the mosquito breeding season, for a 5-day period. When water is thus lowered, grassy edges of lakes are left exposed to sun and dryness, which kill the larvae; when that's done, the level of water is raised again. The dean of a Melbourne engineering school came to look into the cost of producing power and fixing rates. Brazil's Minister of Agri culture was here, and so was Lord Halifax when Ambassador at Washington. A man from India's public works office came, and so did the senior engineer of the Niger River Project in French West Africa.