Why did 28,000 rivers in China suddenly disappear?

For years, China claimed to hold an estimated 50,000 rivers within its borders. Now, more than half of them have abruptly vanished.

Last week, China's Ministry of Water Resources announced the results of a three-year survey of the country’s waterways, revealing startling declines in water supply. According to the census, there were 22,909 rivers in China as of 2011, each covering an area of at least 100 square kilometers. That marks a decrease of about 28,000 from the government's previous estimates, raising fears among environmentalists and putting Beijing on the defensive.

China's longest rivers, the Yangtze and the Yellow, have each seen declining water levels in recent years, but the government's survey — its most comprehensive to date — may shed new light on the breadth and gravity of the country's crisis.

According to the South China Morning Post, officials attributed the decline to global warming and outdated mapping techniques, saying previous estimates were based on incomplete topographical maps from the 1950s. Experts, meanwhile, say there are more direct factors at play — namely, explosive economic development and poor environmental stewardship.

Ma Jun, director of the Beijing-based Institute of Public and Environmental Affairs, acknowledges that updated mapping techniques could explain some discrepancies in river estimates, though he notes that the government's findings corroborate those from independent studies.

source - http://www.theverge.com/2013/4/3/4175514/china-rivers-disappear-from-the-map-water-supply-crisis