Minor changes in punctuation, removal of an article "it," and capitalization were needed to make the sentences correct. The last sentence "it works well in nowadays" is incorrect and best changed to "It works well even today" or "Even today, it works well" to share the idea that it is amazing and awesome that the project runs well after thousands of years. The overall idea was still conveyed well 👍.

Dujiangyan water conservancy project **was** built 2200 years ago. It is a national 5A-level scenic spot, a world cultural heritage site, and one of the oldest water **conservation** projects in the world. It works well nowadays. (There is no “in” before “nowadays”) ((Good job! I agree that it’s a lovely spot. I’ve visited it! ❤️))