In few places on earth can you experience firsthand both the glories of the ancient world and the fragility of our planet today. Seizing on this duality, Jordan has created an extraordinary travel experience that starkly highlights the crucial role of a dwindling resource: water. Susan Hack explores a royal initiative that is transforming the meaning of desert adventure

The horns of the male ibex sweep back like a scimitar and have parallel ridges like growth rings on a tree, guide Mahmoud al Nawasreh is telling me. Each ridge marks a year of the wild mountain goat's life; the wider the spacing, the more water and grazing were available. "Look at this dung beetle," he marvels, pausing to observe a scrabbling, dime-sized insect. Points on its carapace trap morning dew, and when the beetle straightens its backmost pair of legs, droplets flow down into its mouth.

The power of water is Mahmoud's preoccupation during our six-hour hike through the Mujib Nature Reserve, an arid wilderness of limestone crags and banded sandstone gorges on the eastern Dead Sea coast. A flash flood four weeks before my April visit flattened the tamarisk along the banks of the Mujib, one of seven spring-fed rivers that slice through cliffs and ferry salts and minerals to the Dead Sea, the lowest point on earth. This strange, shimmering brine is unable to support anything more complex than bacteria, and against its backdrop of sterility, desert life is a vivid miracle. In the Mujib's pebbly bed, we spot flood survivors: A red crab waves its claws at me, an emerald frog clings to a blade of grass, and a pair of finger-sized yellow- and black-striped fish escort their tiny brood.

Water is my theme, too, during a two-week trip through the Hashemite Kingdom of Jordan, a young country in an ancient civilization that has grown steadily drier over the centuries. In a neighborhood defined by conflicts about land and resources, Jordan is a relative oasis of political stability where water, not oil, holds the key to prosperity. From Neolithic hunter-gatherers, who built the first stone houses near permanent springs ten thousand years ago and began experimenting with crops, to the Nabateans, who built an empire based on the provision of water and food to desert travelers, to the Romans, whose sophisticated hydrology permitted construction of monumental cities such as Jerash, to the Umayyad Caliphs, who built swimming pools and bathhouses in the now-barren Eastern Desert, the connection between water and human endeavor is evident—and relevant—here as nowhere else.

Water is the thrill of the Malaqi Trail, which leads from a hot, sun-exposed plateau down to the shaded floor of Wadi Mujib and the malaq ("junction" in Arabic) of the Mujib and Hidan rivers. After hours of desert walking, I'm now soaking wet, wading chest deep up the Hidan where it narrows between the whorled purple, russet, and mustard walls of a siq, or slot canyon. Placing our backpacks on a dry rock ledge, Mahmoud and I swim or clamber over submerged boulders into a succession of deep pools linked by small, fast-flowing waterfalls.

I've brought a wet suit top to wear with my T-shirt and hiking shorts, but the water is surprisingly warm. Mahmoud explains that the Hidan originates in a hot spring; the Mujib Nature Reserve lies 1,350 feet below sea level, close to steam vents from deep in the earth's crust. I rest in a natural Jacuzzi, a chamber excavated by swirling currents that massage my tired joints. (Hours later, in my simple room at the reserve's ecolodge, I'll feel the ghost sensation of river water pulling at my legs, dragging me sideways, rolling me over.)