India, April 19 -- T hey say: "Follow the river and it will eventually lead you to the sea". This is no longer true in parts of the world. For nearly 6 million years, the Colorado river (right) flowed from the Rocky Mountains into the Gulf of California. Over the past 20 years, it has seen volumes drop by 20%, and it now runs dry almost 160 km before it reaches the sea. Irrigation consumes more than half the river's water, with much of this used to grow cattle-feed crops. Another tenth is claimed by evaporation at dam reservoirs, with another 20% supplied to households and industries. Meanwhile, more than half of the Western United States is currently experiencing drought conditions, following a winter of historically low snow, according to the federal drought monitoring system. As much as 75% of water supplies can come from snowmelt here, which acts as a crucial natural reservoir, as the US Geological Survey has put it in reports. This has resulted in mandatory water restrictions across a wide swathe of the country. In some cities, restaurant owners are being asked to serve water only if patrons ask for it. In certain regions, the watering of lawn has been restricted to no more than twice a week. Amid a record warm winter and a March heatwave, river and stream volumes are dipping further. "This might be what it takes to get us to truly adapt to 21st century realities," Kyle Roerink, executive director of the advocacy group Great Basin Water Network, told The New York Times last week. "If we believe what the top scientists are saying, this isn't the worst it's going to get in the 21st century."...