A dried-up river bed is exposed in Yun county, Shiyan city of Central China's Hubei province, April 11, 2013. The water level at the Yun county section of the Han River, a tributary of the Yangtze River, has been declining mainly due to increased agricultural irrigation and less precipitation, adding to the poor navigation conditions in the upstream area. Local vessel traffic control authorities have taken a variety of measures to ensure marine safety. [Photo/CFP]