'Jordan River Deep and Wide" it isn't. Not any more. It's about 2.5m across and very slow-moving at the one point you can visit these days, a small channel in Bethany. Here, between the Israeli and Jordanian flags, a stone font has been erected to mark the nearest point on the river-bank to the place where John baptised Jesus. Leo Blair was baptised here recently while his father was on one of his many missions to bring peace to the Middle East. Ironically, it was a real peace deal, the one that Jordan signed with Israel in 1994, that enabled archaelogists and tourists once again to visit Bethany and the banks of the Jordan, which had been a military stand-off zone for decades. What they found was not just that the River Jordan had moved several hundred yards west of Christ's original baptism site but that the river itself had dwindled dramatically.
Further north up the rift valley, dams and irrigation initiatives have taken a lot of water out of the Jordan and the results are now clear to everyone, nowhere more so than at the Dead Sea into which the river empties. Stand on top of Mount Nebo today, as Moses did in the Book of Exodus, and you won't see the same Promised Land he did. Jerusalem is still there, but the Dead Sea has definitely retreated. It's now a third of the size it was in 1900. The shrinkage has exposed some great new beaches on the eastern (Jordanian) side of the lake but they symbolise a long-term environmental catastrophe. At the moment the Dead Sea is going down at a rate of one metre a year. In 100 years' time Jordan's new seaside hotels may be left high and dry, bussing people down to the beach.
This is confirmed when I drive up to the Dead Sea Panoramic Complex above Amman Beach. The centre is built out of the distinctive local limestone, shot through with volcanic minerals. It's perched on a rock 800m above sea level. If that doesn't sound impressive enough remember the shores of the Dead Sea are 400m below sea level. The drop truly is vertiginous.
A museum inside the centre explains what's going on. Immediately below us two tectonic plates are parting company. As the African and Arabian plates started to separate 17,000,000 years ago, they formed an enormous rift valley that filled up with water. We know that gap in its latest configuration as the Dead Sea and it's getting bigger because those plates are still diverging. So with the bottom of the sea dropping down gradually, a decrease in river input is the last thing the Dead Sea needs. No wonder when I look down I can see new beaches waiting to emerge from the shallows.
After tea with the director, I head south towards Hammamat Ma'in but something he said stays with me. It seems those two plates aren't just moving apart. The Arabian plate is also heading north. Seventeen million years ago the rocks on which Amman now stands were to the south of the rocks of Jerusalem, then they moved. "Now Amman is to the north of Jerusalem," said my sad man. "And the process is continuing. Every century Amman moves away from Jerusalem the length of a cat." It's quite a thought I agree but, as I drive away, I wish I'd asked him what size of cat.
Hammamat Ma'in is a small park in a valley that runs down to the Dead Sea. Here you can lunch and take turns under two spectacular hot waterfalls that plunge down into the valley from a volcanic fissure - yet more tectonic tourism. The Greeks and Romans had thermal baths here and King Herod (the one who rewarded his pole-dancing stepdaughter with John the Baptist's head) used to come down here for his rheumatism from his castle at nearby Mukawir.
You can still see the site of Mukawir if you want, but the stronghold was seized by rebels in AD70 and so comprehensively smashed up by avenging Romans that not a stone remains. The centurions had every brick thrown down 200m into the valley below.
I chose instead to walk through the nature reserve of Wadi Mujib, which runs down the valley of a Dead Sea tributary. It's a verdant wilderness with three trails, each of which can be traversed by no more than 24 walkers a day. The Mujib river makes a good, if challenging, companion and a certain amount of wading and abseiling is necessary unless you choose your path carefully. However, when I get to the bottom of the wadi, I realise something drastic has happened. A dam has been placed across the valley and the river, instead of flowing into the Dead Sea, is siphoned off into a concrete tunnel turning right up to Amman.
In front of me there is a mass of concrete, a basin built to absorb any excess water during the rainy season but this, I notice, has been smashed. A year ago flood water pummelled the concrete, lifted it up and flung it to one side like a rumpled duvet. It's a reminder that you mess with nature at your peril.
I regain the main road that has been on land vacated by the shrinking sea and cross the Mujib Bridge. Here, above a car park, is a pillar of rock, twisted like a shrill black shriek. This has been known for generations as Lot's Wife, the embodiment of disobedient wives. She looked back as Sodom and Gomorrah fell into the opening chasm of the Dead Sea and was turned into salt. No one put this column here. It was just formed at some vague time in the past, but the moral is clear: don't tamper with the divine plan.
THE COMPACT GUIDE
HOW TO GET THERE:
Adrian Mourby travelled to Jordan with BMED, which can be booked through British Airways (0870-8509 850; ba.com). It offers return flights from London to Amman from around £387. He stayed at the
Kempinski Hotel Ishtar
(00 962 6461 5922; kempinski-deadsea.com) which offers double rooms from £105 per night.
Jordan Tourism Board
(020-7731 6496; visitjordan.com).