As recently as 20 years ago, there were an estimated 50,000 rivers in China, each covering a flow area of at least 60 square miles. But now, according to China's First National Census of Water, more than 28,000 of these rivers are missing. To put this number into context, China's lost rivers are almost equivalent, in terms of basin area, to the United States losing the entire Mississippi River. Why have these rivers "vanished" from the maps and national records?