Peru shields an ancient city of sand from strong storms

JUDY WOODRUFF: Now: a desert that's being overrun by rushing water.

Jeffrey Brown looks at the effort to preserve ancient archaeological sites in Northern Peru against the destructive power of El Nino. It's part of his ongoing series Culture at Risk.

JEFFREY BROWN: It looks like a giant sand castle, its walls and towers slowly being reclaimed by the earth.

This is the ancient city of Chan Chan. Nine square miles-wide, it was once the largest in the Americas and the largest adobe city in the world. It served as the center of political, legislative and religious life for the Chimu people, who ruled this region from the ninth century until the late 1400s, when they were conquered by the Incas.

Here, you get a hint of the splendor before and after restoration of palace ceremonial halls, all of it in one of the driest regions on the planet.

LUIS JAIME CASTILLO, Deputy Minister of Culture, Peru: This is much more of a desert than Saudi Arabia. There's no rain for 15 years, and then one day, boom.

JEFFREY BROWN: Booming, rushing, flooding. These images from February 1998 show the impact of the weather phenomenon known as El Nino at its worst, drenching the region, destroying homes, bridges and endangering the lives of those who live nearby, as well as the thousands of archaeological sites that dot the land here, slicing through centuries-old adobe walls and smearing away paintings more than 1,000 years old.

Peru's deputy cultural minister, Luis Jaime Castillo, was a young archaeologist when one of the most devastating El Ninos hit his country.

LUIS JAIME CASTILLO: In '83, when I was like in my early 20s, the El Nino happened and took everybody by surprise. I mean, we were not prepared. In the past, the Chimu would do lots of human sacrifices to prevent the rain from falling. We cannot do that anymore.

JEFFREY BROWN: No, that's not allowed, even at the Culture Ministry.

LUIS JAIME CASTILLO: No. No. Well, but we can invest some money, which we can put, unleash the archaeologists to do their work.

JEFFREY BROWN: It can look as simple and as daunting as this, a local worker with a syringe squirting water into a crack to reinforce an adobe wall.

Imagine how many injections are required for this huge area. But the work is going on. After climatologists predicted a strong El Nino for this winter and spring, the government for the first time put in place a plan at a cost of $8 million, hiring around 1,000 workers.

One wheelbarrow at a time — heavy equipment isn't allowed here — they're transporting sand to shore up walls, to prevent water from accumulating and breaking through. They're also building roofs for murals and especially vulnerable areas and laying extensive drainage systems.

Outside the site itself, riverbanks are being fortified and paths cleared for water to flow.

FRANCISCO CHAVEZ, Monterey Bay Aquarium Research Institute: My mother told me a story about when we lived in Northern Peru where the water was up to our knees in our house.

JEFFREY BROWN: Peruvian-born Francisco Chavez would grow up to study El Nino patterns as an oceanographer now at Monterey Bay Aquarium Research Institute in California.

We met in Lima, where he told me what is and still isn't understood about the phenomenon.

FRANCISCO CHAVEZ: We understand the coupling between what happens a long way away from here, like in the Western Pacific, and what happens in Peru. So, we have come a long way.

At the same time, we're still at the point where it's very difficult for us to predict the timing and the magnitude of these events.

JEFFREY BROWN: El Ninos occur on average every five years, when the typically cool surface temperatures of the equatorial Pacific Ocean warm, altering weather patterns in Peru and other parts of the world, including in the U.S.

They have happened for centuries. The Chimu in Chan Chan certainly experienced them. The Spanish name in fact came from Peruvian fisherman, who in the northern port of Huanchaco still use traditional reed boats like this. Warmer waters tend to come around Christmas, hence the association with El Nino, the baby Jesus.

A definitive link with climate change remains elusive, but Francisco Chavez say scientists are now seeing a new phenomenon.

FRANCISCO CHAVEZ: What we think we can say is that the changes that we're seeing recently are of larger amplitude in both directions. And so if that pattern continues, then, over the next 15 to 20 years, we will see a number of very large El Ninos.

JEFFREY BROWN: Not far Chan Chan, against a dusty mountain backdrop, another dramatic site, Huaca de la Luna, the Temple of the Moon.

Nestled at the base of Cerro Blanco, the White Mountain, this was a huge sacred complex of the Moche people, who preceded the Chimu from about 100 to 800 A.D. On an exterior wall, level upon level of elaborately sculpted and patients murals of mythic gods, humans and animals, including from the nearby ocean.

Ricardo Morales is co-director of the site and one of Peru's leading conservators.

RICARDO MORALES, Huaca de la Luna (through interpreter): They're not just pictures and decorations. They're forms of communication that tell a story through an image.

JEFFREY BROWN: But here, too, the faces of gods washed away is evidence of damage from previous El Ninos. And here, too, the preservation work goes on, as workers use a local species of cane to build roofs to divert the coming rains and uncover new murals and treat them with protective chemicals.

Morales told us that modern conservators can actually learn from the ancients, who after all had themselves faced El Nino devastation. Here, it's new technology mixed with the old.

RICARDO MORALES (through interpreter): El Nino teaches us there are types of adobe. The brown type most resistant to rains. So we have developed a prototype, so we now have a more rain-resistant adobe that we're using to protect the sites and that people are now using in their homes.

JEFFREY BROWN: The Moche knew how to deal with El Nino and you're learning from them.

RICARDO MORALES (through interpreter): Yes.

JEFFREY BROWN: Yes.

RICARDO MORALES (through interpreter): All these structures are knowledge. We take advantage of ancient knowledge and these improve techniques using modern construction.

JEFFREY BROWN: On the colorful main square of the nearby city of Trujillo, another kind of construction was under way, as the Star of Bethlehem and Christmas decorations went up to celebrate El Nino himself.

As Christmas approached, this area may be getting a break. The latest forecast have downgraded the severity of the imminent El Nino. But everyone told us there's really no way to know for sure. All they can do is prepare and perhaps pray to the gods of old.

From Northern Peru, I'm Jeffrey Brown for the "PBS NewsHour."