A new study says the world’s major river systems contain more than enough water to meet global food production needs in the 21st century. Following a five-year study of 10 river basins — including the Nile, Ganges, Andes, Yellow, and Niger — scientists with the Consultative Group on International Agricultural Research (CGIAR) found that the greatest water challenge facing the planet is not scarcity but the inefficient and inequitable distribution of water. “Huge volumes of rainwater are lost or never used,” said Alain Vidal, director of CGIAR’s Challenge Program on Water and Food. In regions of sub-Saharan Africa, he said, even “modest” improvements in rainwater harvesting could yield two to three times more food production. Elsewhere, regions in Asia and Latin America exist where food production could be increased by at least 10 percent, according to the report, which is published in the journal Water International. According to a recent UN report, global food output will have to increase 70 percent by 2050 to feed a growing world population.