Nelson Ramírez, health secretary for the rural Colombian town of Sibaté, is used to battling mosquitoes. They surge up from the heavily polluted waters of the nearby Muña Reservoir, and swarm every night into residents’ homes—Ramírez’s included. He stops up his doors with rags, seals his windows and sprays insecticide. But he is losing the battle. Neither those measures nor the omnipresent mosquito traps hung from lampposts seem to do any good in this town, which is located 17 miles (28 kms) downriver of Bogotá. Muña, built in 1948 to impound water from the Bogotá River for two hydroelectric plants, seems cursed. The Bogotá’s once-clean waters now receive 190,000 tons a year of residential and industrial waste upstream of the reservoir. Muña, in... [Log in to read more]