I believe that the correct translation into English would be something along the lines on, "I have become thirsty," as 了 acts as a particle for a change in the state of something. However, as "I have become thirsty" sounds a little odd, at least to my ears, a better translation would be "I am thirsty" or "Now I am thirsty (whereas I wasn't thirsty before).
You could also say 我很渴 or even 我渴死了 (literally "I am thirsty to death").
Please go to #465911.
This sentence has been deleted because it was a duplicate.