Tengger dunes with the wall in the foreground

About 25 kilometres west of the city of Zhongwei, the Yellow River emerges from its steep-sided canyon (see One Step Forward, Two Steps Back), and for the next several hundred kilometres the river flows across a wide floodplain. Under natural conditions, the river would have flooded and spread across this plain annually, dumping the sediment picked up from its journey through the mountains to create deep soils.

Although it doesn’t rain much here (a bit over 18 cm annually), the flat terrain, fertile soil and easy access to water make the area perfect for irrigation. Over the past few millenia a series of cultures, not all of them Chinese, have lived on and farmed this floodplain. The wall was built along the perimeter of the agricultural area, protecting the fields from invaders and, coincidentally, separating them from the Tengger Desert to the north.

The wall and a beacon tower, northeast of Zhongwei

Unlike some of the arid country we’ve been through before, the Tengger is classic desert – endless waves of sand dunes broken only by the occasional rocky crag. It seems devoid of life, but we were lucky enough to see a critter we call the Wall Owl. Wall Owls seem to be fairly similar to North American burrowing owls: they’re active during the daytime, likely live in burrows (as there are no trees to nest in), and probably feed on rodents and the large insects (beetles and desert cicadas) that run around on the dunes. We’ve seen them often on the drier portions of our route, but the little guys rarely sit still long enough for a portrait.

Perched on the wall

The dunes at 4 pm

The wall climbs over a hill that juts out from the sand

While the dunes may be good hunting grounds for owls, they’re not so great for railway transportation when they migrate over the tracks. In order to ensure the free passage of trains along the Baotou-Lanzhou railway line, the Shapotou Desert Research Station of the Chinese Academy of Sciences has managed a dune stabilisation project in the area since 1956. To begin with, straw checkerboards one meter square are placed in the dunes, then after four or five years drought-tolerant shrubs are planted along the checkerboards.

The Shapotou dune stabilisation project. You can see the electrical lines of the railway in the upper left corner of the photo.

The poor wall, however, does not merit this kind of effort. In some places it’s buried completely beneath the sand and we can follow it only by walking from beacon tower to beacon tower. In other places some remnants are visible, but only just.

A tower pokes through the dunes

The crest of the wall with sand piled along the sides