Washington (AFP) – The massive Colorado River, which provides water for seven US states, has seen its flow reduced by 20 percent over the course of a century — and more than half of that loss is due to climate change, according to new research published Thursday.Two scientists at the US Geological Survey developed a mathematical model of the water movements — snowfall, rainfall, run-off, evaporation — in the upper Colorado River basin for the period from 1913 to 2017.To do so, they used historical temperature and precipitation data, along with satellite readings of radiation, in order to un…