If it's wet and flat enough to farm, someone lives there.
The Yangbi area is inhabitated by a minority nationality called the Bai (white).
Photo by Ben Foster.
This expedition was the first for Earth Science Expeditions. It had originally planned a first descent of the mainstream Mekong for October, 1989, but the Tienanmen Square incident in June caused it to cancel. The Chinese Academy of Sciences contacted ESE in 1992 about reapplying for permits, but it took two years to organize the expedition and permit fees for the main stream were too high so they compromised by running the Yangbi. Between 1987, when Pete Winn and Mike Connelly first drove to the put-in, and 1994 when they returned with two 16' catarafts, three kayaks and a total of 8 people, the Chinese had built a paper mill on a tributary that drained Er Hai (Ear Lake) into the Yangbi, and the river was full of foam - not an auspicious start. Also, in 1987 the Chinese had begun construction of the Man Wan Dam near the take-out, and by 1994 the dam was completed and the reservoir was full.
The put-in was southwest of Dali near 25.491614°, 99.982473°, 4300', the average gradient was about 12' per mile and trip length was about 80 miles to the confluence with the Mekong, near 24.717095°, 100.094009°, 3300', and 70 miles across the new reservoir to the Man Wan Dam (24.621996°, 100.446331°). In October, the flow was about 2500 cfs. Most of the river was Class 2-3, with a couple of Class 4s. In 2004, some of the same team revisted Dali, on the shores of Er Hai, on their way back from a first descent of the Mekong in Tibet, only to hear that most of the Yangbi had been dammed. This is no longer a feasible run.
See Yangbi First Descent by Pete Winn for details.