Sedimentology

Down to the river

PUBLISHED : Tuesday, 14 February, 2012, 12:00am
UPDATED : Tuesday, 14 February, 2012, 12:00am

After almost two weeks of walking along the Great Wall, we finally reached the edge of a huge valley, which we descended on a road of swerving switchbacks. About halfway down, we looked across a gully to see another Great Wall watchtower, so we scrambled across to it, and as we arrived, gasping, at its base, there it was below us: Huang He, the mighty Yellow River.

I had seen the Yellow River once before - in the city of Jinan, when I was cycling down the east coast about seven years ago. There, near the river's mouth, the river was a turgid, brown-yellow mass, and in the stifling, humid summer air, it looked almost boiling. Here, in the middle course, the river was a deep grey and brown colour.

We could see a huge dam upstream across the river, which was frozen solid, although below the dam, the river was flowing again. Huge cliffs well over 100 metres high encased the river, and, as we followed it as part of our 5,000 kilometre walking expedition, we saw a series of twisting cliff roads, villages and occasional factories that ran along the top.

The Yellow River is known as the 'mother of China' because through the millennia it has fertilised and irrigated the land, and it is here that China's earliest documented civilisations arose. But it's also known as 'the sorrow of China', because of its propensity for regular and terrible floods, which through the centuries are thought to have killed millions of people.

The reason for the floods is that the river carries huge quantities of sediment - mostly loess, the soft yellow earth of the river's upper and middle reaches. In fact, it carries more than 36kg of sediment per cubic metre of water, compared with the less than 2kg by the Nile. This sediment is then deposited on the riverbed downstream, meaning the bed is always rising, and so huge embankments are needed to control the river.

While the huge number of dams built in the past 50 years have tamed the river somewhat, it still poses many challenges, not least that the silt is always clogging up the dams. What's more, due to pollution, half of its water is now considered biologically dead, and because of excessive use, since the late 1970s the river has often run dry before it even reaches the sea.

We hiked down the side of the hill to the water's edge and followed a path that led to the next village about 10 kilometres downstream. That night we camped in a flat area of small trees, rather nervous about the following day because we would have to walk along a treacherous slope of loose rock beneath the high cliffs and above the icy river.

We picked our way along the scree for much of the morning. Blocked by sheer cliffs ahead of us, we had to follow a gully high up into the hills again, through a scattering of villages. Eventually, we found a road that led us down, two days later, to Hequ county on the east side of the Yellow River in northwest Shanxi province. A smart car pulled up just as we approached the city centre, and a friendly man invited us back to his family house for dumplings and wine.

From Hequ we continued south along the river. Another 50 kilometres downstream, it finally became a flowing body of water, full of massive blocks of ice and snow, and mostly frozen along its edges.

We had planned to carry portable inflatable kayaks and use them when we reached the river. However, we abandoned the plan earlier on in the expedition as the delays so far meant that the river was going to be dangerously frozen in parts. As we walked along the river, I thought it was the right decision because there was quite a high risk of drowning in the unfrozen parts.

This week, we will reach the incredible Hukou Waterfall, where we will cross into Shaanxi, the neighbouring province of Shanxi, and head to the ancient capital of Xian.

Rob Lilwall's previous expedition, Cycling Home From Siberia, became the subject of an acclaimed motivational talk, a book, and a National Geographic television series. Every week in Health Post, he will write about the progress of his new expedition, Walking Home From Mongolia, which is in support of the children's charity Viva. www.walkinghomefrommongolia.com