Why is Changan’s weather in Xichang always clear?

Does the questioner want to ask "Why is Chang'an always short of water due to the weather in Xichang?" Problems such as lack of water sources and insufficient water supply. Xichang has low rainfall and relatively scarce water resources, which will lead to problems such as lack of water sources and insufficient water supply, resulting in poor water quality or clean water supply. In addition, there may also be problems with local water treatment facilities, pipeline systems and other facilities, resulting in unstable water quality and difficulty in ensuring water cleanliness.