It just occurred to me that Jesus lived in the middle-east, where there's not much water. Alcohol dehydrates you by making you pee more, and Jesus was supposed to be a man of the people- that is, someone focussed on helping people get from day to day. So doesn't it seem counter-productive to turn water into wine? Wouldn't it actually be more characteristic/benevolent to turn wine into water? Or was it all just to show off his superpowers and that's seen as more impressive?
Jesus was supposed to be a man of the people- that is, someone focussed on helping people get from day to day.
Why do you think so? Jesus came to redeem people by his suferring and death. Not to make their life comfortable.
Jesus lived in the middle-east, where there's not much water
Water was not scarce in Jesus's place and during his time. I don't know where you got that data from. Water was an integral part of temple ceremony and was lavishly used during sacrifice. Also Water Into Wine miracle narrative itself records there were six stone jars full of water present there just to be used in ceremonial washing. That is how much water they had. There is no contemporary record showing that water was scarce. After all, Jerusalem was supposed to be a land flowing with milk and honey.
So doesn't it seem counter-productive to turn water into wine? Wouldn't it actually be more characteristic/benevolent to turn wine into water?
No. Wine was an integral part of Jewish marriage custom at the time. Not providing sufficient wine was an insult to the guests and thereby a shame to the newly wed. Jesus helping them in their need is in fact a "characteristic/benevolent" act.
Was it all just to show off his superpowers and that's seen as more impressive?
Have you read the Gospel narrative? Vast majority of people who attended the wedding including the master of the banquet did not know where the wine came from. So your claim of show off his superpowers doesn't hold good.
When Jesus turned water into wine, He performed His first miracle at the wedding feast. It was also at the request of His mother. He didn't want to demonstrate His power yet, but still obeyed His mother. It shows how Christians must respect Mary as Christ did.
This first miracle also foreshadowed His death on the cross as being the sacrificial lamb. To explain, during the Last Supper, Jesus and His disciples did not eat the traditional passover meal as all Jews would have. They did not eat a sacrificed lamb - Jesus became that perfect lamb who was broken on the cross. What at first seems strange, they also did not drink all the different cups of wine required during the meal. When Jesus drank the vinegar wine on the cross, He stated "It is finished." This was the final cup of the passover meal. When Jesus died, He completed the passover meal on the cross.
The first miracle of turning water into wine was bookended with Him becoming the passover feast. Christians and His Church are the Bride of Christ. The events in the New Testament correlate for very specific reasons to demonstrate His divinity and salvation.
Jesus commanded that we must eat of His flesh and drink His blood. This was not symbolic. Many of His disciples left because they could handle His command. In Communion, Jesus becomes the bread and wine in Mass. This belief was even understood by the pagans in the first centuries and was only disputed over 1000 years after Christ. Peter commanded that you cannot have communion in a state of sin, otherwise you drink and eat condemnation upon yourself. The miracle when Jesus multiplied the bread and fish also ties into how during Mass how Christians can still eat His flesh and drink His blood.
To be a Christian, you must believe in the actual presence of Christ in Communion. It is a core belief, not something optional. This is why Jesus turned the water into wine - and how he "turns Himself" into wine in Communion.
Uta Ranke-Heinemann, among others, points out the parallels to pagan tradition in the account of Jesus turning water into wine. She says, in Putting Away Childish Things that the transformation of water into wine is a typical motif of the Dionysus legend, in which this miracle serves to highlight the god's epiphany. On his feast day, Dionysus made empty jars fill up with wine in his temple in Elis; and on the island of Andros, wine flowed instead of water from a spring or in his temple.
A similar example, also in John's Gospel, at John 5:1-9, where Jesus cured the lame man at the pool with five porches, near the sheep market outside Jerusalem. Archaeologists have found that pool, still with a votive offering to the Greek god of healing, Asclepius. This was an Asclepium, or temple to Asclepius. As was typical of his temples around the Greek world, whenever he came by and disturbed the water, whoever was first to enter the water would be cured. In both examples, John has portrayed Jesus as being capable of doing with great ease whatever the pagan gods could do. So these examples were to show off Jesus' powers, although it was not Jesus doing this but the author of John, and the audience for the miracle was John's readers, not people at a wedding.
At http://en.wikipedia.org/wiki/Dionysus#Parallels_with_Christianity, we find Peter Wick cited as saying, "... the use of wine symbolism in the Gospel of John, including the story of the Marriage at Cana at which Jesus turns water into wine, was intended to show Jesus as superior to Dionysus."