Evaporation blamed on global warming has reduced Lake Titicaca, one of the world's highest navigable lakes, to its lowest level since 1949, authorities said Thursday. Diminished rainfall and a rise in solar radiation have in the past four years led to critically low water levels that now threaten fish spawning areas and plant life, the Lake Titicaca Authority said in a statement. Titicaca's waters have dropped 81 centimeters (2.65 feet) since April and flora and fauna are apt to suffer damage if they drop another 30 centimeters (one foot), the statement said. Navy Capt. Jorge Ernesto Espinoza told ATB television that South America's largest lake is receding by 2 to 3 centimeters (about an inch) a week. The lake, straddling Bolivia and Peru at 3,800 meters (12,493 feet) elevation, is an 8,400 square kilometer (3,240 square mile) oasis on an arid high plain an hour's drive from the Bolivian capital, La Paz. The lake is fed by rainfall and melt water from glaciers, which scientists say are shrinking rapidly due to global warming and could disappear altogether by mid-century. About 2.6 million people depend on the lake for their sustenance. The Titicaca Authority says 95 percent of the lake's inflow is now evaporating. One reason is that the area's rainy season has been reduced from six to three months, said Felix Trujillo, chief of Bolivia's National Meterological and Hydrological Service. He said this year's rainy season is expected to begin in mid-November. The drought has prompted water rationing in some Bolivian cities. Environment Minister Rene Orellana said Bolivia needs $1 billion over the next seven years to build reservoirs that will guarantee an adequate water supply. 