Water evaporates at a lower temperature in lower air pressure.
Simple law of physics that no one seems to be noticing, or if they are then they are ignoring it when confronted with disappearing lakes;

http://www.earth-policy.org/Updates/2005/Update47.htm

and drying rivers.

Some of the world's largest and best-known rivers are at risk of drying up as a result of climate change, pollution and bad planning, a report warned today.
The study by the environment group, WWF, focuses on the ten rivers most danger of drying up or dying, and warns that, without action, the world faces "a freshwater emergency".
Five of the 10 rivers listed are in Asia, including the Yangtze, the Ganges and the Salween, highlighting the profound problems facing the region.
Europe's Danube, the African Nile and South America's Rio Grande are among other rivers under serious threat.