Northern Lao - European
The two expedition teams returned with in total 13.5 km of surveyed cave passage in Laos and 2.5 km in Myanmar.The Houaphan team continued in a new area north of Xam Neua which was only briefly visited on the last day of the 2012 expedition. The area proved to have a high potential with a number river caves exceeding 1 km in length, the longest being Tham Nam Oogh at 3 km. Several caves still continue, e.g. Tham Houay Ngot, another underground stream left in open passage where the team mapped 1,850 m of passage. The river flowing through this cave is suspected to connect to Tham Giga, which was a record-breaking discovery of the Houaphan team representing the largest cave passage found so far in Northern Laos: although only 350 m long, the main gallery of Tham Giga partly measures 90 m in width and 50 m in height. Other connections of caves north of Xam Neua appears to be likely. A brief reconnaissance trip to other villages in the area confirmed the existence of more underground rivers and large fossil caves. Access to the caves north of Xam Neua partially requires long hikes with luggage. The constantly cold and foggy weather during the dry season also contributes to make it a challenging area for caving in Northern Laos. In total, about 8.8 km of cave passages were mapped north of Xam Neua. The team spent its final week in the well-known area of Viengxai east of Xam Neua, where access to new caves has been improved by new infrastructure. Several new caves and historical man-made caverns were added to the long list of caves in this beautiful tower karst. This includes Tham Fam, a fine underground stream about 1.1 km long. About 3.2 km of new cave passages were harvested around Viengxai and the area was again left with a good number of more caves noted but left for a future visit.
The objective of the Nong Khiaw team was to revisit and to continue the survey of the Tham Doun Mai which was surveyed to a length of 2,000 m beyond a large chamber of 100 m length and 50-60 m height and was left in wide open passage in 2012. The 2013 expedition surveyed another 1.7 km until the terminal sump was reached. The cave has a very diverse character including a fossil upper level with beautiful formations, a sportive section at the river level dominated by water and cascades, followed by classical big river passages with a meandering stream and ending in an upward-trending passage with challenging climbs in active waterfalls. With 3.7 km of length Tham Doun Mai is currently the 4th longest cave in Northern Laos.
The recce to Myanmar targeted the Pinlaung river valley in Southern Shan State. Here the Namun spring cave which is the resurgence of a larger karst area was first described by Dunkley in 1989 and the entrance confirmed in 2005 by La Venta. The team got access to the restricted area and surveyed 1.2 km of passage. It is an system determined by large overflow passages with an underlying stream. The water volumes in rainy season are estimated large and in an order of 100 cm/s.The sink of Te Toke Taung is about 5 km in distance and still undescended. Other caves in the same area were surveyed as well and revisit to the Hopong area done. In total 2.5 km were mapped.
Follow-up in the areas of Laos and Myanmar will be discussed while the team is meeting during the International Caving Conference in Brno July 2013.