Discovery of the World's Longest Underground River

In 1997, Peter took part in an expedition that mapped 13,817 meters of the giant Hang Khe Rhy (Grass Stream Cave).

View Photos (5) Image © 2000 Alan Richardson

A Scottish student has used the skills learned in getting his university degree to discover the world's longest underground river. Peter MacNab, 30, has just returned from a month-long caving expedition to Vietnam where he discovered the longest cave in mainland Southeast Asia, through which runs what is thought to be the world's longest underground watercourse--the Son Trach River.

Situated in the Bo Trach district of the Vietnamese province of Quang Binh, the route to the cave entrance involved a daylong drive along the crater-ridden Ho Chi Minh trail in a Russian-built transporter. This was followed by an eight-hour trek through dense jungle foliage, using machetes to clear a path to the cave entrance.

Now in his fourth year of the Construction Management course at the University of Abertay Dundee, Peter used the land surveying and management skills learned in his studies to map previously uncharted areas of the giant Hang Khe Rhy cave, deep in the heart of the Vietnamese jungle.

The Abertay Dundee student used a compass, Global Positioning System (GPS), tape measure and clinometer to measure the cave, known as the "Grass Stream Cave" and the river to the nearest 10 centimeters.

Maps produced by MacNab will play a crucial part in the government's bid to have the Phong Nha massif (the area in which the cave lies) recognized as a United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage Site. He explained: "We were invited by Hanoi University, which is working in conjunction with the Vietnamese government to have this area recognized as a World Heritage Site before the new millennium." In 1998, UNESCO's World Heritage Committee added 30 new sites to its World Heritage List of cultural and natural sites, bringing the total of listed sites of "exceptional universal value" to 582 in 114 countries. It is hoped that later this year, the Phong Nha massif will take its place on UNESCO's World Heritage List.

"The Phong Nha massif contains a myriad of spectacular river caves. It is one of the few areas in the world that has not been affected by climate change or human activity and there are many species of animals indigenous to the area such as the Francois Langur monkey--of which there are only 2,000 left in the world."

Construction Management program tutor Nick Hamilton of the University of Abertay Dundee's School of Science and Engineering, commented: "Peter has always been an excellent student and when he puts his mind to something, you can bet that he will achieve it. All Peter's hard work over the past few months--he completed his dissertation a month early so he could undertake this expedition--has certainly paid off with this historic achievement."

The team of ten British cavers, four Vietnamese and two Australians, plus six porters, painstakingly measured and mapped 18,902 meters of Hang Khe Rhy cave. In addition, the team showed that the Son Trach River measures a record-breaking seven miles in length, surpassing the previous record for the world's longest underground river claimed by the five-mile-long St. Paul River in the Philippines' region of Palawan.

Throughout the expedition, the team, which included doctors, zoologists and geologists in its ranks, spent 12 days underground in Hang Khe Rhy, at times forced to plunge into the icy Son Trach River in a bid to complete their journey. Why does he do it? "It's a part of the world where no one has ever been before. And if no one's ever been there, you don't know what you're likely to find," he said. "Our aim is to make a landmark discovery in modern-day caving and so push back the boundaries of the earth's final frontier."

The group has been invited to return in 2001 to explore other cave systems in the Phong Nha massif. Later this year, archaeologists will visit Hang Khe Rhy to search for prehistoric remains.

Peter and his wife, Anette, first met on a caving trip to Spain. Last month she traveled to Vietnam with Peter and was part of the Hang Khe Rhy expedition team. Expedition leader Howard Limbert commented: "Peter and Anette have a great partnership and kept everyone's spirits up during the trip. Hang Khe Rhy and the river that runs through it, is truly remarkable and, due to its remote situation, should remain in pristine condition for years to come."

MacNab, who took up the sport 19 years ago, is an experienced caver, whose reputation precedes him in British caving circles. His love of caving has seen him circle the globe over recent years, taking in the Philippines, Indonesia, Austria and Spain.

The most memorable moment of the trip for Peter was when the team located the cave exit, christened "Huda Thought It." He said: "Emerging into broad daylight after days underground was simply amazing. The cave exit was 50 meters high and rattan vines hung down to the entrance floor. It was like a scene from an Indiana Jones movie."

Published on 7/1/99