how can i cross to thirsty river?

someone know or tell me the way how can i cross to thirsty river
and what mission i need to do to reach thare ?
thanking you in advance
barak.

You need to walk to Thirsty River. No mission will take you there. You can either just explore the desert slowly, and then discover Thirsty River more or less by accident, or you can look at one of the maps available on the internet (do a search for guildwars maps for example) to locate where Thirsty River is.

You also can pay someone to run you there, but its up to you whether you want to utilize this form of transportation, which I myself never use.